If your OBD-II scanner displays P0077, your vehicle’s Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected a higher-than-expected electrical signal in the Bank 1 intake valve control solenoid circuit.
The generic OBD-II definition for P0077 is:
Intake Valve Control Solenoid Circuit High Bank 1
Depending on the manufacturer or scan tool, the description may appear as:
- Intake Valve Control Solenoid Circuit High Bank 1
- Intake Valve Timing Control Solenoid Circuit High Bank 1
- Intake Camshaft Control Solenoid Circuit High Bank 1
- Intake Oil Control Valve Circuit High Bank 1
- Variable Valve Timing Solenoid Circuit High Bank 1
- Intake Valve Control Solenoid Open or Short to Battery Bank 1
P0077 is an electrical circuit code involving the solenoid that controls oil flow to the Bank 1 intake camshaft actuator. On certain Hyundai and Kia applications, manufacturer diagnostic information describes P0077 as an intake oil-control-valve circuit that is open or shorted to battery voltage.
Common causes include:
- Disconnected intake valve control solenoid
- Open solenoid coil
- Broken control wire
- Signal circuit shorted to battery voltage
- Corroded or loose connector terminals
- Missing PCM control of the circuit
- Incorrect replacement solenoid
- Failed PCM driver
Possible symptoms include:
- Check Engine Light
- Rough or unstable idle
- Poor acceleration
- Hesitation
- Reduced engine power
- Increased fuel consumption
- Hard starting
- Engine stalling
- Failed emissions inspection
- No noticeable drivability symptoms
Because P0077 affects the variable valve timing system, the PCM may disable intake camshaft adjustment and leave the camshaft in a default position until the electrical fault is repaired.
For additional diagnostic information, visit:
P0077 Quick Facts
| Item | Information |
|---|---|
| OBD-II Code | P0077 |
| Description | Intake Valve Control Solenoid Circuit High Bank 1 |
| Category | Powertrain |
| System | Variable Valve Timing |
| Main Component | Intake Valve Control Solenoid |
| Affected Side | Bank 1 |
| Fault Type | High Circuit Voltage |
| Common Electrical Cause | Open Circuit or Short to Battery |
| Severity | Moderate |
| Safe to Drive? | Sometimes, for a short distance |
| Typical Repair Cost | $100–700 |
What Does P0077 Mean?
P0077 means the PCM sees voltage or circuit feedback that is higher than expected in the Bank 1 intake valve control solenoid circuit.
The affected circuit may include:
- Intake valve control solenoid
- Solenoid power-supply wire
- PCM control wire
- Electrical connector
- Shared fuse or relay
- Engine wiring harness
- PCM output driver
Depending on circuit design, P0077 may be triggered by:
- An open solenoid coil
- A disconnected electrical connector
- A broken wire
- A control wire shorted to battery voltage
- Excessive resistance in the circuit
- An incorrect solenoid
- A failed PCM driver
A Hyundai diagnostic reference for P0077 describes the detection strategy as an electrical check for an open circuit or short to battery, with the fault detected when the control circuit remains at battery voltage instead of responding correctly to PCM control.
P0077 is primarily an electrical code. Engine-oil condition still matters because the solenoid controls hydraulic oil flow, but dirty oil alone does not explain a control circuit that remains electrically high.
What Is Bank 1?
Bank 1 is the side of the engine containing cylinder number 1.
On an inline engine, such as an inline four-cylinder or inline six-cylinder, there is only one cylinder bank. That bank is Bank 1.
On a V-type engine, Bank 1 may be located on either side depending on the engine’s cylinder-numbering layout.
Bank 1 is not automatically:
- Driver side
- Passenger side
- Front of the engine
- Left side
- Right side
Use the correct:
- Cylinder-numbering diagram
- Factory service information
- Repair manual
- Underhood emissions label
to identify Bank 1.
Replacing the Bank 2 solenoid because it was easier to reach may improve access to your wallet, but it will not repair P0077.
What Is an Intake Valve Control Solenoid?
The intake valve control solenoid is an electrically operated oil-control valve used by the engine’s variable valve timing system.
Depending on the manufacturer, it may also be called:
- VVT solenoid
- Oil control valve
- Intake valve timing control solenoid
- Intake camshaft actuator solenoid
- Variable camshaft timing solenoid
- VCT solenoid
- CVVT oil control valve
- Intake timing control valve
The solenoid regulates pressurized engine oil flowing to the intake camshaft actuator or cam phaser.
This allows the PCM to change intake camshaft timing according to:
- Engine speed
- Engine load
- Throttle position
- Coolant temperature
- Oil temperature
- Vehicle speed
- Requested torque
- Emissions strategy
Variable intake camshaft timing can improve:
- Low-RPM torque
- High-RPM power
- Fuel economy
- Idle quality
- Cold-start performance
- Turbocharger response
- Exhaust emissions
P0077 does not necessarily mean the camshaft actuator itself has failed. It means the PCM has detected an electrical problem in the circuit controlling the intake solenoid.
How Variable Valve Timing Works
The variable valve timing system changes when the intake valves open and close relative to crankshaft position.
A typical system includes:
- Engine oil supply
- Oil passages in the cylinder head
- Intake valve control solenoid
- Intake camshaft actuator or phaser
- Camshaft position sensor
- Crankshaft position sensor
- PCM control strategy
When the PCM commands a timing adjustment:
- The solenoid changes position
- Pressurized oil is routed to the camshaft actuator
- The actuator rotates the camshaft slightly relative to its sprocket
- Intake valve timing advances or retards
- The camshaft sensor reports the actual position
- The PCM compares desired timing with actual timing
If the PCM cannot electrically control the solenoid because the circuit is open or held at excessive voltage, it may store P0077 and disable variable valve timing.
How the Intake Valve Control Solenoid Circuit Works
Many intake VVT solenoids use two electrical terminals.
A common design includes:
- Battery or ignition voltage supplied to one terminal
- PCM-controlled ground connected to the other terminal
The PCM controls solenoid current by rapidly switching the ground side using pulse-width modulation.
The PCM may monitor:
- Control circuit voltage
- Current draw
- Coil resistance
- Driver feedback
- Commanded duty cycle
- Circuit response when switched on or off
When the PCM commands the circuit low but the voltage remains high, it may interpret the condition as:
- Open circuit
- Disconnected solenoid
- Broken control wire
- Short to battery voltage
- Failed PCM driver
Other vehicles may use a high-side control circuit, so the exact meaning of “circuit high” must be confirmed using the correct wiring diagram.
What Does “Circuit High” Mean?
“Circuit high” means the PCM sees electrical voltage or feedback above its expected range.
It does not necessarily mean:
- Engine oil pressure is high
- Engine temperature is high
- Camshaft timing is over-advanced
- Intake valve lift is excessive
- Battery voltage is generally too high
The fault concerns the monitored solenoid circuit.
Common circuit-high conditions include:
- Solenoid disconnected
- Open solenoid coil
- Broken control wire
- Open power or return path
- Control circuit shorted to battery voltage
- Corroded terminal creating excessive resistance
- PCM driver unable to pull the circuit low
On many low-side-controlled circuits, an open connection leaves the control wire near supply voltage. The PCM sees that the circuit remains high when it should have been pulled toward ground.
P0075 vs P0076 vs P0077
| Code | Description | Typical Meaning |
| P0075 | Intake Valve Control Solenoid Circuit Bank 1 | General electrical circuit malfunction |
| P0076 | Intake Valve Control Solenoid Circuit Low Bank 1 | Circuit voltage below expected range |
| P0077 | Intake Valve Control Solenoid Circuit High Bank 1 | Circuit voltage above expected range |
Related Bank 2 codes include:
| Code | Description |
| P0081 | Intake Valve Control Solenoid Circuit Bank 2 |
| P0082 | Intake Valve Control Solenoid Circuit Low Bank 2 |
| P0083 | Intake Valve Control Solenoid Circuit High Bank 2 |
P0077 does not automatically prove that the solenoid is bad.
The failure may be located in the:
- Connector
- Wiring harness
- Fuse or relay
- Solenoid coil
- PCM control circuit
- PCM itself
P0077 vs P0010
P0010 is generally defined as:
“A” Camshaft Position Actuator Circuit Bank 1
P0077 is defined as:
Intake Valve Control Solenoid Circuit High Bank 1
Depending on manufacturer terminology, both codes may involve the Bank 1 intake camshaft oil-control solenoid.
The difference is that P0077 specifically identifies a high electrical circuit condition, while P0010 is a broader actuator-circuit malfunction.
Vehicle-specific service information should determine:
- Which component is involved
- Which terminal should have power
- How the PCM controls the circuit
- What voltage threshold triggers the code
How the PCM Detects P0077
The PCM may set P0077 when:
- Control circuit voltage remains too high
- The circuit remains near battery voltage when commanded on
- The solenoid coil is electrically open
- The solenoid connector is disconnected
- The control wire is broken
- The control circuit is shorted to battery voltage
- Current flow is lower than expected
- Driver feedback does not match the command
On one documented Hyundai circuit, the PCM runs the electrical check with battery voltage within a defined operating range and can identify a short-to-battery condition within approximately two seconds. Thresholds and timing vary by vehicle.
The PCM may respond by:
- Illuminating the Check Engine Light
- Disabling intake VVT operation
- Storing freeze-frame data
- Entering failsafe mode
- Fixing the intake camshaft in a default position
Symptoms of P0077
Possible symptoms include:
- Check Engine Light
- Rough idle
- Unstable idle speed
- Engine hesitation
- Poor throttle response
- Reduced acceleration
- Loss of low-end torque
- Reduced high-RPM power
- Increased fuel consumption
- Hard starting
- Extended cranking
- Engine stalling
- Misfires
- Increased exhaust emissions
- Failed emissions inspection
- Reduced-power mode
- No noticeable symptoms
Reduced performance, increased fuel consumption, rough running, and occasional starting problems are commonly associated with P0077 and loss of intake-camshaft control.
Symptoms depend on:
- Engine design
- Default camshaft position
- Whether the circuit is permanently open
- Whether the solenoid is mechanically stuck
- Whether additional timing codes are present
- Oil condition
- Camshaft actuator condition
Some engines continue running reasonably well with VVT disabled.
Others feel as though the powerband has been replaced with a gently worded suggestion.
Can P0077 Cause a Rough Idle?
Yes.
If the PCM cannot control the intake camshaft, the camshaft may remain in a position that is not ideal for idle.
Possible results include:
- Rough idle
- Surging
- Low manifold vacuum
- Misfires
- Stalling
- Poor cold-start operation
However, rough idle can also be caused by:
- Vacuum leaks
- Ignition faults
- Fuel-injector problems
- Mechanical timing faults
- Camshaft sensor failure
- Low compression
Confirm that the P0077 circuit fault is active before blaming every idle complaint on the VVT system.
Can P0077 Cause Poor Acceleration?
Yes.
Variable intake camshaft timing helps optimize cylinder filling across different engine speeds and loads.
If VVT operation is disabled, the engine may lose:
- Low-speed torque
- Midrange response
- High-RPM power
- Turbocharger response
- Fuel efficiency
The PCM may also limit engine output if it cannot verify safe camshaft control.
Common Causes of P0077
1. Disconnected Intake Valve Control Solenoid
A disconnected solenoid is one of the most common causes of a circuit-high fault.
The connector may have been left unplugged during:
- Valve-cover replacement
- Timing-chain service
- Cylinder-head repair
- Engine replacement
- Intake manifold work
- Oil-leak repair
- Previous VVT diagnosis
A disconnected connector prevents current flow and may leave the monitored circuit at supply voltage.
2. Open Solenoid Coil
The electrical coil inside the solenoid may break.
Possible causes include:
- Age
- Thermal cycling
- Engine vibration
- Internal corrosion
- Manufacturing defect
- Heat damage
An open coil normally measures:
- Infinite resistance
- Extremely high resistance
- No continuity
The PCM may detect that no current flows when the solenoid is commanded.
3. Broken PCM Control Wire
The control wire may break because of:
- Engine vibration
- Harness tension
- Heat
- Improper routing
- Rodent damage
- Previous repair
- Connector strain
A broken wire commonly causes:
- Open circuit
- High control-circuit voltage
- No solenoid current
- P0077
The conductor may be broken inside insulation that still appears intact.
4. Control Circuit Shorted to Battery Voltage
The PCM control wire may contact:
- Ignition-voltage wiring
- Injector power circuit
- Solenoid power circuit
- Alternator wiring
- Battery-positive cable
- Incorrectly installed accessory wiring
Manufacturer-oriented diagnostic references specifically associate P0077 with an open circuit or short to battery in the intake oil-control-valve circuit.
A short to voltage can prevent the PCM from pulling the control circuit low and may damage the PCM driver.
5. Loose Solenoid Connector
A connector that is not fully locked may cause:
- Intermittent open circuit
- Excessive resistance
- Low current
- P0077
- Related P0075 faults
Inspect for:
- Broken locking tab
- Missing secondary retainer
- Connector not fully seated
- Loose terminal fit
- Damaged connector body
6. Corroded Connector Terminals
Corrosion can increase resistance enough to prevent proper current flow.
Inspect for:
- Green deposits
- White oxidation
- Darkened terminals
- Water
- Oil contamination
- Bent pins
- Spread terminals
- Damaged seals
Poor connections and damaged connectors are recognized common causes of P0077.
7. Backed-Out Connector Terminal
A terminal may be pushed backward when the connector is installed.
It may appear connected externally while failing to contact the solenoid pin.
Check for:
- Uneven terminal depth
- Broken retaining tang
- Missing secondary lock
- Terminal movement
- Weak pin contact
A backed-out terminal can make the circuit electrically identical to an unplugged solenoid.
8. Oil Inside the Connector
Engine oil may enter the connector because of:
- Solenoid seal failure
- Valve-cover leak
- Oil migration through the solenoid
- Harness contamination
Oil can:
- Damage seals
- Trap dirt
- Reduce terminal contact
- Wick through the wiring harness
- Contribute to intermittent resistance
Repair the leak and replace contaminated terminals or pigtails when necessary.
9. Heat-Damaged Wiring
VVT wiring may be routed near:
- Exhaust manifold
- Turbocharger
- EGR components
- Cylinder head
- Hot coolant pipes
Heat may cause:
- Brittle insulation
- Melted wires
- Open conductors
- Circuits fused together
- Short to voltage
Inspect missing or damaged heat shields.
10. Chafed Wiring Harness
The harness may rub against:
- Valve-cover edge
- Cylinder-head casting
- Engine bracket
- Intake manifold support
- Wiring tray
- Metal retaining clip
A chafed wire may alternately:
- Open
- Short to ground
- Short to voltage
depending on engine movement.
11. Incorrect Previous Wiring Repair
Poor repairs may include:
- Twisted wires covered with tape
- Unsealed butt connectors
- Incorrect wire gauge
- Weak crimp
- Cold solder joint
- Incorrect connector pinout
- Repair wire routed against heat
A weak connection may add enough resistance to create a circuit-high code.
12. Incorrectly Wired Replacement Connector
A replacement pigtail may have:
- Reversed terminals
- Incorrect cavity assignment
- Wrong wire connected to PCM control
- Loose crimps
- Incorrect terminal type
Always verify the connector pinout using the wiring diagram.
Matching colors is useful, but previous repairs may have already converted the harness into an automotive guessing game.
13. Failed Intake Valve Control Solenoid
The solenoid may fail electrically or mechanically.
Electrical failures include:
- Open coil
- Internal terminal break
- Excessive resistance
- Intermittent internal connection
- Short to housing
Mechanical failures include:
- Stuck spool valve
- Sludge buildup
- Varnish
- Metal contamination
- Blocked screen
P0077 points first toward the electrical circuit, but a complete diagnosis should also inspect the solenoid mechanically after the circuit is tested.
14. Incorrect Replacement Solenoid
An incorrect solenoid may have:
- Wrong coil resistance
- Different connector pinout
- Incorrect oil-port arrangement
- Different operating frequency
- Poor internal construction
An aftermarket solenoid may physically fit while remaining electrically incompatible.
That is not an upgrade. It is a more polished method of storing the same code.
15. Missing PCM Ground Control
On a low-side-controlled circuit, the PCM must ground the solenoid to energize it.
If the PCM cannot pull the circuit low, causes may include:
- Open control wire
- Loose PCM terminal
- Failed PCM driver
- PCM power or ground problem
- Software fault
- Driver protection caused by a previous short
The solenoid supply side may test correctly while the control side remains at battery voltage.
16. Poor PCM Connector Connection
The PCM connector may have:
- Corrosion
- Bent terminal
- Backed-out pin
- Water intrusion
- Loose locking lever
- Damaged seal
- Poor terminal tension
Inspect the PCM only after disconnecting the battery and following manufacturer procedures.
17. Blown Fuse or Failed Relay
Circuit design matters.
A failed fuse or relay more commonly removes supply voltage and may trigger a general circuit code, but some monitoring strategies can report a high or open condition when current does not flow as expected.
If several engine actuators have codes, inspect:
- Shared actuator fuse
- PCM relay
- Ignition relay
- Common power splice
Do not replace multiple solenoids before checking the one fuse they all share.
18. High Circuit Resistance
A partially broken wire or corroded terminal may allow voltage to appear on a multimeter while preventing sufficient current flow.
Possible sources include:
- Corroded splice
- Loose connector
- Weak crimp
- Heat-damaged terminal
- Broken wire strands
- Worn relay contact
A loaded voltage-drop test is more useful than a simple continuity test.
19. Low Engine Oil Level
Low oil level is not normally the direct cause of the high electrical signal.
However, it can cause:
- Poor VVT response
- Camshaft timing codes
- Phaser noise
- Solenoid sticking
- Oil aeration
Low oil is frequently listed among broader VVT-system conditions that should be checked during P0077 diagnosis.
Always inspect oil level before commanding the VVT system.
20. Dirty or Sludged Engine Oil
Dirty oil may restrict:
- Solenoid spool movement
- Solenoid screen
- Cylinder-head oil passages
- Camshaft actuator movement
Dirty oil more commonly causes timing-performance codes than a circuit-high code, but it can coexist with an electrically damaged solenoid.
An oil change will not repair an open wire, though it may give the technician something cleaner to lean over while finding it.
21. Incorrect Oil Viscosity
Oil that is too thick or too thin can reduce VVT performance.
Possible effects include:
- Slow camshaft movement
- Poor cold-start response
- Low hot-idle oil pressure
- Cam phaser noise
- Related timing-performance codes
Use the manufacturer-specified:
- Oil viscosity
- Oil standard
- Oil filter
22. Clogged Solenoid Screen
Some VVT solenoids contain a fine oil screen.
It may become restricted by:
- Sludge
- Varnish
- Metal particles
- Gasket debris
- Excessive silicone sealant
A clogged screen does not normally create an open electrical circuit, but it may explain continued timing problems after P0077 is repaired.
23. PCM Software Issue
A software or calibration problem may cause the PCM to:
- Misinterpret circuit feedback
- Command the solenoid incorrectly
- Set P0077 prematurely
- Fail to clear failsafe operation
Check for:
- Technical service bulletins
- Calibration updates
- Reprogramming instructions
- Revised diagnostic procedures
Software issues are less common than connector, wiring, and solenoid faults.
24. Failed PCM Driver
The internal PCM driver may fail because of:
- Short to battery voltage
- Shorted solenoid
- Excessive current
- Water intrusion
- Internal electronic failure
A damaged driver may be unable to ground or control the solenoid circuit.
Only suspect the PCM after confirming:
- Correct solenoid resistance
- Correct supply voltage
- Control-circuit continuity
- No short to battery
- Connector integrity
- PCM powers and grounds
- Correct software level
Replacing the PCM before checking whether the solenoid connector is plugged in is automotive diagnostics sponsored by unnecessary expense.
Is P0077 Serious?
P0077 is generally considered a moderate-severity code.
The engine may continue running, but intake camshaft timing may become:
- Disabled
- Fixed in a default position
- Unable to follow PCM commands
- Inconsistent with engine load
Possible consequences include:
- Reduced power
- Rough idle
- Poor fuel economy
- Increased emissions
- Hard starting
- Engine stalling
- Failed emissions inspection
P0077 becomes more serious if:
- Oil-pressure warning light is illuminated
- Engine oil is extremely low
- Engine rattles or knocks
- Vehicle stalls
- Misfires are severe
- Wiring is overheating
- Multiple timing or correlation codes are stored
- The vehicle enters reduced-power mode
Can You Drive With P0077?
You may be able to drive a short distance if:
- Engine oil level is correct
- Oil-pressure warning light is off
- Engine runs reasonably smoothly
- No severe mechanical noise is present
- Acceleration remains safe
- Wiring is not overheating
Avoid continued driving if:
- Oil-pressure warning light is on
- Engine rattles
- Vehicle stalls
- Power is severely reduced
- Wiring smells burned
- Multiple camshaft correlation codes are present
- Engine will not start reliably
P0077 usually will not destroy the engine immediately.
Continuing to drive with low oil pressure or severe timing noise because the scanner mentioned a solenoid is a far more ambitious risk.
How to Diagnose P0077
Step 1: Scan for All Stored Codes
Check for:
- P0075
- P0076
- P0077
- P0010
- P0011
- P0012
- P0081
- P0082
- P0083
- Camshaft position codes
- Crankshaft position codes
- Oil-pressure codes
- System-voltage codes
- Misfire codes
Record:
- Freeze-frame data
- Pending codes
- Permanent codes
- Engine RPM
- Battery voltage
- Oil temperature
- Commanded VVT duty cycle
- Desired camshaft angle
- Actual camshaft angle
Do not clear the codes before recording diagnostic information.
Step 2: Confirm Bank 1
Identify:
- Cylinder number 1
- Bank 1 cylinder head
- Bank 1 intake camshaft
- Correct intake valve control solenoid
Do not confuse:
- Bank 1 with Bank 2
- Intake solenoid with exhaust solenoid
- VVT solenoid with camshaft position sensor
- Oil-pressure switch with oil-control valve
Step 3: Check Engine Oil Level
Park the vehicle on level ground.
Verify:
- Oil level
- Oil condition
- Correct viscosity
- Signs of leakage
- Oil-pressure warning-light behavior
Correct low oil before operating or testing the VVT system.
Step 4: Inspect Oil Condition
Look for:
- Sludge
- Varnish
- Fuel dilution
- Coolant contamination
- Metal debris
- Excessively thick oil
- Incorrect oil viscosity
Perform an oil and filter change when needed, but continue electrical diagnosis because P0077 specifically identifies a circuit-high fault.
Step 5: Locate the Bank 1 Intake Solenoid
The solenoid is commonly mounted:
- In the cylinder head
- Near the valve cover
- Near the timing cover
- At the front or rear of the cylinder head
- Beneath an engine cover
- Near an intake camshaft oil passage
Use service information to verify the component.
Step 6: Confirm the Connector Is Attached
Before testing anything complicated, verify that the connector is:
- Installed
- Fully seated
- Locked
- Not swapped with another connector
- Free from broken tabs
P0077 is often caused by an open or disconnected solenoid circuit.
This simple inspection can prevent a lengthy diagnostic journey toward a connector visibly hanging beside the solenoid.
Step 7: Inspect the Solenoid Connector
Disconnect the connector and check for:
- Bent pins
- Corrosion
- Oil contamination
- Water intrusion
- Backed-out terminals
- Spread terminals
- Heat damage
- Missing seals
Repair connector damage before replacing the solenoid.
Step 8: Inspect the Wiring Harness
Follow the wiring toward the PCM and power distribution system.
Look for:
- Broken wires
- Chafing
- Melted insulation
- Pinched sections
- Rodent damage
- Poor repairs
- Contact with exhaust components
- Missing harness retainers
- Wiring stretched across brackets
Pay special attention to the first several inches behind the connector.
Step 9: Measure Solenoid Resistance
Disconnect the solenoid and measure resistance across its terminals.
Compare the measurement with factory specifications.
Possible findings include:
- Infinite resistance: open coil
- Excessively high resistance: damaged coil or internal connection
- Resistance below specification: shorted coil
- Correct resistance: continue circuit diagnosis
Generic resistance specifications should not be substituted for vehicle-specific data.
Step 10: Check Each Terminal Against the Solenoid Housing
When service information permits, measure resistance between each solenoid terminal and its metal body.
Unexpected continuity may indicate:
- Internal short
- Coil insulation failure
- Contamination inside the solenoid
Step 11: Reconnect or Substitute a Known-Good Solenoid
When approved, connect:
- A known-good solenoid
- A manufacturer-specified test load
- An appropriate resistor or test lamp
Observe whether circuit status changes.
If P0077 changes or the monitored circuit returns to normal, the original solenoid may have an open coil.
Use only a test load appropriate for the PCM driver.
Step 12: Verify Solenoid Power Supply
With the ignition on, identify and test the power-supply terminal.
Depending on circuit design, expected voltage may be:
- Battery voltage
- Ignition voltage
- Relay-controlled voltage
- PCM-controlled voltage
If power is missing, inspect:
- Fuse
- Relay
- Power wire
- Shared splice
- Connector terminal
Step 13: Load-Test the Power Circuit
A high-impedance multimeter may display normal voltage even through a severely corroded connection.
Use an approved load test to check:
- Relay contacts
- Fuse terminals
- Power splices
- Connector pins
- Supply wiring
Excessive voltage drop indicates resistance in the circuit.
Step 14: Test the PCM Control Wire for an Open
Disconnect the PCM and solenoid as instructed.
Measure continuity through the control wire.
Check for:
- Infinite resistance
- Excessive resistance
- Intermittent connection
- Broken splice
- Incorrect terminal position
Move the harness while monitoring resistance.
Step 15: Test for a Short to Battery Voltage
With the PCM and solenoid disconnected, test whether the control wire receives voltage from another circuit.
Possible sources include:
- Solenoid power feed
- Injector power circuit
- Ignition circuit
- Alternator wiring
- Damaged accessory wiring
A short to battery is a documented P0077 detection condition on some applications.
Step 16: Test for a Short Between Wires
Inspect whether the control circuit is shorted to:
- Another VVT circuit
- Fuel-injector wiring
- Ignition-coil wiring
- Heated oxygen-sensor wiring
- Charging-system wiring
Heat damage can fuse several wires together inside an otherwise normal-looking harness.
Step 17: Check Connector Terminal Tension
Use the manufacturer-approved terminal test tool.
Check for:
- Spread terminal
- Weak contact
- Backed-out pin
- Broken retaining tang
- Incorrect replacement terminal
Poor terminal tension can create an intermittent open that stores P0077.
Do not insert an oversized meter probe directly into the connector and manufacture the failure yourself.
Step 18: Perform Voltage-Drop Testing
With the circuit operating, test voltage drop across:
- Power-supply wire
- Fuse
- Relay contacts
- Solenoid connector
- PCM control wire
- PCM grounds
Excessive voltage drop indicates unwanted resistance.
Step 19: Command the Solenoid With a Scan Tool
Use a bidirectional scan tool when supported.
Monitor:
- Solenoid command
- Duty cycle
- Control voltage
- Current draw
- Desired intake camshaft angle
- Actual intake camshaft angle
- Engine idle speed
Possible results include:
- No current flow: open solenoid or open wiring
- Control circuit remains high: open wire, short to voltage, or failed PCM driver
- Electrical circuit responds but camshaft does not move: hydraulic or mechanical problem
- Timing moves correctly: intermittent fault or stored history code
Step 20: Use a Current Clamp
A low-current clamp can measure solenoid current without opening the circuit.
Possible findings include:
- Zero current: open circuit
- Lower-than-normal current: excessive resistance
- Excessive current: shorted coil
- Unstable current: intermittent connection
Compare with:
- Manufacturer specifications
- Known-good Bank 2 solenoid
- Identical known-good vehicle
Step 21: Examine the Control Signal With an Oscilloscope
An oscilloscope can show:
- Pulse-width-modulated signal
- Duty cycle
- Voltage amplitude
- Driver switching
- Electrical noise
- Intermittent dropouts
A circuit that remains near battery voltage while commanded may indicate:
- Open control wire
- Disconnected solenoid
- Open solenoid coil
- Short to voltage
- Failed PCM driver
Step 22: Perform a Wiggle Test
Monitor live circuit data while moving:
- Solenoid connector
- Harness near the valve cover
- Wiring near exhaust components
- Fuse-box connectors
- PCM connector
- Previous repair areas
Watch for:
- Voltage changes
- Current appearing or disappearing
- Code status changing
- Engine idle changing
- Camshaft command returning
Step 23: Inspect the Solenoid Mechanically
If the electrical circuit is repaired but VVT performance remains poor, remove the solenoid.
Inspect for:
- Sludge
- Varnish
- Metal debris
- Damaged screen
- Stuck spool valve
- Broken O-ring
- Silicone contamination
Mechanical restrictions are more likely to cause P0011, P0012, or similar performance codes than P0077 alone.
Step 24: Compare Bank 1 With Bank 2
On engines with two banks, compare:
- Solenoid resistance
- Supply voltage
- Control waveform
- Current draw
- Desired camshaft timing
- Actual camshaft timing
Bank 2 can provide a useful reference if both circuits use identical components and control strategies.
Step 25: Swap Solenoids Only When Approved
If the Bank 1 and Bank 2 intake solenoids are confirmed identical, a controlled swap may help isolate the fault.
After swapping:
- Code moves to Bank 2: solenoid likely faulty
- Code remains on Bank 1: wiring or PCM circuit likely faulty
Do not swap intake and exhaust solenoids unless the manufacturer confirms they are interchangeable.
Step 26: Check PCM Power and Grounds
Before condemning the PCM, verify:
- Constant battery power
- Ignition power
- PCM grounds
- Connector condition
- Terminal tension
- Water intrusion
- System voltage
A PCM ground problem may interfere with driver operation and circuit monitoring.
Step 27: Check Technical Service Bulletins
Search manufacturer information using:
- VIN
- Model year
- Engine code
- P0077
- Solenoid part number
- PCM calibration number
- Related codes
Possible factory corrections include:
- Updated solenoid
- Revised connector
- Harness-routing repair
- PCM calibration update
- Revised diagnostic procedure
Step 28: Evaluate the PCM Driver
Only evaluate PCM failure after confirming:
- Solenoid resistance is correct
- Solenoid connector is secure
- Power supply is correct
- Control wire has continuity
- Control wire is not shorted to battery
- PCM power and ground are correct
- No connector damage is present
If the PCM cannot switch the circuit and all external wiring tests pass, the driver may require:
- Software update
- Module repair
- PCM replacement and programming
Step 29: Verify the Repair
After completing repairs:
- Clear all diagnostic trouble codes.
- Start the engine.
- Confirm normal oil-pressure warning-light operation.
- Monitor the intake solenoid command.
- Check circuit voltage and current.
- Compare desired and actual camshaft timing.
- Check idle quality.
- Road-test the vehicle under varied load and RPM.
- Complete the required drive cycle.
- Rescan for pending and confirmed codes.
- Confirm P0077 does not return.
Common Repairs and Costs
| Repair | Estimated Cost |
| Reconnect or reseat solenoid connector | $0–100 |
| Clean electrical connector | $50–150 |
| Replace connector terminals | $75–250 |
| Engine oil and filter change | $60–180 |
| Replace intake valve control solenoid | $150–500 |
| Repair open or shorted wiring | $150–650 |
| Replace solenoid connector | $100–325 |
| Repair engine power-supply circuit | $150–700 |
| Replace fuse or relay after repairing fault | $75–250 |
| Clean restricted oil passage | $200–700 |
| Replace camshaft actuator or phaser | $700–2,000+ |
| Replace timing-chain components | $1,000–4,000+ |
| Update PCM software | $100–300 |
| Replace and program PCM | $1,000–2,500+ |
Actual repair cost depends on:
- Vehicle model
- Engine design
- Solenoid accessibility
- Wiring location
- Labor rate
- Whether additional VVT faults exist
- Whether module programming is required
A disconnected solenoid may require only a few seconds to repair.
An open control wire hidden beneath the intake manifold may require the patience normally reserved for archaeology.
Common Diagnostic Mistakes
Avoid these common P0077 diagnostic mistakes:
- Assuming “circuit high” means high oil pressure
- Replacing the solenoid without testing its coil
- Ignoring a disconnected connector
- Failing to identify Bank 1 correctly
- Confusing intake and exhaust solenoids
- Testing only the power wire
- Failing to test the PCM control wire
- Ignoring a short to battery voltage
- Checking continuity without load-testing the circuit
- Using generic solenoid resistance specifications
- Replacing the camshaft phaser before testing the electrical circuit
- Replacing the PCM before checking connector terminals
- Ignoring oil level and condition
- Installing an incorrect aftermarket solenoid
- Failing to verify the repair with scan-tool commands
P0077 is an electrical circuit-high code.
Replacing the timing chain because the engine has variable valve timing skips several cheaper and considerably more relevant diagnostic steps.
Vehicles Commonly Affected
P0077 is a generic OBD-II code and may appear on various vehicles, including certain:
- Hyundai vehicles
- Kia vehicles
- Nissan vehicles
- Infiniti vehicles
- Mazda vehicles
- Mitsubishi vehicles
- Toyota vehicles
- Lexus vehicles
- Subaru vehicles
- Ford vehicles
- Lincoln vehicles
- Chevrolet vehicles
- GMC vehicles
- Cadillac models
- Dodge vehicles
- Jeep models
- Chrysler vehicles
Manufacturer terminology may include:
- Intake oil control valve
- Intake valve timing control solenoid
- CVVT oil control valve
- VCT solenoid
- Camshaft actuator solenoid
- Intake VVT solenoid
P0077 diagnostic information is particularly documented on Hyundai and Kia applications, where the PCM may set the code when the oil-control-valve circuit is open or shorted to battery voltage.
Always use the correct service procedure for the vehicle and engine.
P0077 on Hyundai and Kia Vehicles
Hyundai and Kia may refer to the component as the:
- Intake oil control valve
- CVVT oil control valve
- Intake valve control solenoid
On certain applications, the PCM controls the oil control valve using a duty-cycle signal and monitors the circuit for:
- Open wiring
- Short to battery voltage
- Poor connection
- Failed oil control valve
The documented diagnostic logic may identify the fault quickly when battery voltage is within the expected operating range.
Important inspection areas include:
- Solenoid connector
- Wiring near the cylinder head
- Solenoid coil resistance
- PCM control wire
- Oil level and condition
- PCM connector
P0077 on Nissan and Infiniti Vehicles
Nissan commonly calls the component the:
Intake Valve Timing Control Solenoid Valve
Possible causes include:
- Open solenoid coil
- Disconnected connector
- Broken ECM control wire
- Harness short to voltage
- Corroded terminal
- ECM driver fault
- Incorrect replacement solenoid
Oil condition and oil pressure should also be checked if additional intake timing-performance codes are stored.
P0077 After Engine Repairs
If P0077 appears after:
- Valve-cover replacement
- Cylinder-head work
- Timing-chain repair
- Engine replacement
- Intake manifold removal
- Solenoid replacement
inspect for:
- Solenoid connector left unplugged
- Connector attached to wrong component
- Harness pinched beneath a bracket
- Terminal pulled from connector
- Incorrect solenoid installed
- Power and control wires reversed
- PCM connector not fully locked
A code that appears immediately after repair work should be investigated first in the area that was disturbed.
The PCM is sophisticated, but it still cannot plug in the connector the technician forgot.
P0077 After Replacing the VVT Solenoid
If P0077 appears after installing a new solenoid, check:
- Correct part number
- Correct Bank 1 location
- Connector fully seated
- Terminal alignment
- Coil resistance
- Pigtail wiring
- O-ring installation
- Bent solenoid pins
A new component may be:
- Incorrect
- Defective
- Electrically incompatible
- Installed on the wrong bank
Do not assume the PCM failed because the newly installed part arrived in a box.
Can Dirty Oil Cause P0077?
Dirty oil can contribute to mechanical VVT problems, but P0077 specifically identifies a high electrical circuit condition.
Dirty oil may cause:
- Solenoid spool sticking
- Restricted oil screen
- Slow camshaft response
- P0011 or P0012
- Cam phaser noise
Dirty oil does not directly repair or explain:
- Disconnected connector
- Open solenoid coil
- Broken control wire
- Short to battery voltage
Check oil condition, but do not abandon electrical diagnosis.
Can a Bad VVT Solenoid Cause P0077?
Yes.
A VVT solenoid can cause P0077 if its internal coil is:
- Open
- Excessively resistive
- Intermittently disconnected
- Damaged at an internal terminal
Measure coil resistance and compare it with manufacturer specifications.
Can a Bad Camshaft Position Sensor Cause P0077?
A camshaft position sensor is not a common direct cause of P0077.
The camshaft sensor reports camshaft position, while P0077 monitors the intake valve control solenoid circuit.
A bad camshaft sensor is more likely to set:
- Camshaft position sensor code
- Camshaft correlation code
- Timing-performance code
- Starting or stalling complaint
Diagnose all stored codes together.
How to Prevent P0077
Reduce the likelihood of P0077 by:
- Keeping engine oil at the correct level
- Using the correct oil viscosity
- Following recommended oil-change intervals
- Repairing oil leaks promptly
- Keeping solenoid connectors clean and dry
- Replacing damaged connector seals
- Reinstalling engine-harness retainers
- Keeping wiring away from exhaust heat
- Inspecting wiring after engine repairs
- Using OEM-quality VVT solenoids
- Avoiding oversized electrical test probes
- Repairing damaged wiring before it shorts to voltage
Frequently Asked Questions
What does P0077 mean?
P0077 means the PCM has detected a higher-than-expected electrical signal in the Bank 1 intake valve control solenoid circuit.
What is the full definition of P0077?
The generic definition is:
Intake Valve Control Solenoid Circuit High Bank 1
Where is Bank 1?
Bank 1 is the side of the engine containing cylinder number 1.
An inline engine has only one bank, which is Bank 1.
What does circuit high mean?
Circuit high means the monitored electrical voltage or driver feedback is above the PCM’s expected range.
Common causes include:
- Open circuit
- Disconnected solenoid
- Broken control wire
- Short to battery voltage
- Failed PCM driver
Does circuit high mean high engine oil pressure?
No.
The word “high” refers to the electrical circuit signal, not engine-oil pressure.
What causes P0077 most often?
Common causes include:
- Disconnected solenoid connector
- Open solenoid coil
- Broken control wire
- Short to battery voltage
- Corroded connector
- Failed intake VVT solenoid
- PCM driver problem
Is P0077 serious?
P0077 is moderately serious.
The engine may continue running, but performance, fuel economy, idle quality, and emissions may be affected.
Can I drive with P0077?
Possibly for a short distance if:
- Engine oil level and pressure are normal
- Engine runs reasonably well
- No severe noise is present
- Power loss is mild
Stop driving if the oil-pressure light is on, the engine rattles, it stalls, or power loss is severe.
Can P0077 cause a rough idle?
Yes.
Loss of intake camshaft control may cause rough idle, surging, misfires, or stalling.
Can P0077 cause poor acceleration?
Yes.
The engine may lose torque and throttle response if intake valve timing cannot be adjusted.
Can an unplugged VVT solenoid cause P0077?
Yes.
A disconnected solenoid commonly creates an open circuit and may leave the monitored circuit at a high voltage.
Can broken wiring cause P0077?
Yes.
An open control wire or a wire shorted to battery voltage can set P0077.
Can a bad connector cause P0077?
Yes.
Loose, backed-out, corroded, or oil-contaminated terminals can interrupt current flow and cause a circuit-high fault.
Can dirty oil cause P0077?
Dirty oil can contribute to mechanical VVT problems, but P0077 requires electrical testing because it identifies a circuit-high condition.
What is the difference between P0075 and P0077?
P0075 indicates a general Bank 1 intake valve control solenoid circuit malfunction.
P0077 specifically indicates that the circuit signal is above the expected range.
What is the difference between P0076 and P0077?
P0076 indicates a low circuit condition, often involving a short to ground or shorted coil.
P0077 indicates a high circuit condition, often involving an open circuit or short to battery.
Can I test the VVT solenoid with a multimeter?
Yes.
Common tests include:
- Coil resistance
- Continuity
- Short to housing
- Supply voltage
- Control-wire continuity
- Short to battery voltage
- Voltage drop
Use vehicle-specific specifications.
Can I apply battery voltage directly to the solenoid?
Only if the manufacturer’s test procedure permits it.
Incorrect polarity, continuous power, or excessive current can damage the solenoid or wiring.
Does a replacement VVT solenoid require programming?
Usually not.
The vehicle may require:
- Code clearing
- Drive cycle
- Camshaft relearn
- Oil service
- PCM adaptation
A replacement PCM requires programming.
How much does P0077 cost to repair?
A basic solenoid replacement typically costs approximately $150–500.
Wiring, connector, PCM, camshaft actuator, or timing-system repairs may cost substantially more.
Final Thoughts
The P0077 code means the PCM has detected a high electrical condition in the Bank 1 intake valve control solenoid circuit.
The most common causes include:
- Disconnected intake VVT solenoid
- Open solenoid coil
- Broken PCM control wire
- Control circuit shorted to battery voltage
- Loose or corroded connector
- Incorrect replacement solenoid
- Failed PCM driver
Start diagnosis by:
- Scanning for related codes.
- Identifying Bank 1 correctly.
- Checking oil level and condition.
- Confirming the solenoid is connected.
- Inspecting connector terminals.
- Measuring solenoid resistance.
- Verifying supply voltage.
- Testing control-wire continuity.
- Checking for a short to battery voltage.
- Commanding the solenoid with a bidirectional scan tool.
- Evaluating the PCM only after external circuits pass.
Do not interpret “circuit high” as high oil pressure or over-advanced valve timing.
P0077 is warning that the electrical circuit remains above its expected voltage. On many systems, that means the circuit is open, the solenoid is disconnected, or the PCM control wire has found an unwanted source of battery voltage.
The repair may be as simple as reconnecting one plug.
It may also involve finding a broken wire buried beneath a collection of engine covers apparently designed to ensure that every two-minute electrical repair begins with 45 minutes of plastic removal.
Related Articles
Related Camshaft Timing Codes
- P0010 Code Explained: “A” Camshaft Position Actuator Circuit Bank 1
- P0011 Code Explained: “A” Camshaft Timing Over-Advanced Bank 1
- P0012 Code Explained: “A” Camshaft Timing Over-Retarded Bank 1
- P0016 Code Explained: Crankshaft–Camshaft Correlation Bank 1 Sensor A
Previous P-Code Articles
- P0074 Code Explained: Ambient Air Temperature Sensor Circuit Intermittent
- P0075 Code Explained: Intake Valve Control Solenoid Circuit Bank 1
- P0076 Code Explained: Intake Valve Control Solenoid Circuit Low Bank 1
Browse the complete Pro Street diagnostic libraries:
