If your OBD-II scanner displays P0079, your vehicle’s Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected a lower-than-expected electrical signal in the Bank 1 exhaust valve control solenoid circuit.
The generic OBD-II definition for P0079 is:
Exhaust Valve Control Solenoid Circuit Low Bank 1
Depending on the manufacturer or scan tool, the description may appear as:
- Exhaust Valve Control Solenoid Circuit Low Bank 1
- Exhaust Valve Timing Control Solenoid Circuit Low Bank 1
- Exhaust Camshaft Control Solenoid Circuit Low Bank 1
- Exhaust Oil Control Valve Circuit Low Bank 1
- Exhaust VVT Solenoid Circuit Low Bank 1
- Exhaust Valve Control Solenoid Short to Ground Bank 1
P0079 is an electrical circuit code associated with the solenoid that controls oil flow to the Bank 1 exhaust camshaft actuator. The PCM uses this solenoid to advance or retard exhaust camshaft timing as part of the engine’s variable valve timing system.
On documented Hyundai applications, P0079 may be set when the exhaust valve control solenoid control circuit is shorted to ground. Manufacturer-specific detection logic and thresholds vary, so the correct wiring diagram remains essential.
Common causes include:
- Internally shorted exhaust VVT solenoid
- PCM control wire shorted to ground
- Damaged or melted engine wiring
- Corroded connector terminals
- Missing solenoid power supply
- Blown fuse or failed relay
- Incorrect replacement solenoid
- Failed PCM driver
Possible symptoms include:
- Check Engine Light
- Rough or unstable idle
- Poor acceleration
- Reduced engine power
- Hesitation
- Increased fuel consumption
- Hard starting
- Engine stalling
- Failed emissions inspection
- No noticeable drivability symptoms
P0079 is generally considered a moderate-severity fault. The vehicle may remain drivable, but the PCM may disable exhaust camshaft adjustment and hold the camshaft in a default position until the circuit problem is repaired.
For additional diagnostic information, visit:
P0079 Quick Facts
| Item | Information |
|---|---|
| OBD-II Code | P0079 |
| Description | Exhaust Valve Control Solenoid Circuit Low Bank 1 |
| Category | Powertrain |
| System | Variable Valve Timing |
| Main Component | Exhaust Valve Control Solenoid |
| Affected Side | Bank 1 |
| Fault Type | Low Circuit Voltage |
| Common Electrical Cause | Short to Ground |
| Severity | Moderate |
| Safe to Drive? | Sometimes, for a short distance |
| Typical Repair Cost | $100–700 |
What Does P0079 Mean?
P0079 means the PCM has detected an electrical value below its calibrated operating range in the Bank 1 exhaust valve control solenoid circuit.
The monitored circuit may include:
- Exhaust valve control solenoid
- Solenoid power-supply wire
- PCM-controlled ground wire
- Electrical connector
- Shared fuse or relay
- Engine wiring harness
- PCM output driver
Depending on the electrical design, a low circuit condition may indicate:
- Control circuit shorted to ground
- Solenoid coil shorted internally
- Excessive solenoid current
- Missing or severely reduced supply voltage
- PCM driver held permanently low
- Connector terminals bridged together
- Damaged wiring touching the engine
A logged P0079 code generally means there is a low-voltage electrical problem affecting the Bank 1 exhaust valve control solenoid circuit.
P0079 should be diagnosed electrically before replacing camshaft phasers, timing chains, or other mechanical components.
Important Correction: P0078 vs P0079 vs P0080
The correct generic sequence is:
| Code | Description |
| P0078 | Exhaust Valve Control Solenoid Circuit Bank 1 |
| P0079 | Exhaust Valve Control Solenoid Circuit Low Bank 1 |
| P0080 | Exhaust Valve Control Solenoid Circuit High Bank 1 |
Therefore:
- P0078 is the general Bank 1 exhaust solenoid circuit code.
- P0079 identifies a circuit-low condition.
- P0080 identifies a circuit-high condition.
P0079 is not normally the intermittent version of P0078. It specifically refers to a low electrical signal in the exhaust valve control solenoid circuit.
What Is Bank 1?
Bank 1 is the side of the engine containing cylinder number 1.
On an inline engine, there is only one cylinder bank, so the entire engine is considered Bank 1.
On V-type engines, such as a:
- V6
- V8
- V10
- V12
Bank 1 may be on either side of the engine.
It is not automatically:
- Driver side
- Passenger side
- Front side
- Left side
- Right side
Consult:
- Factory service information
- Cylinder-numbering diagram
- Underhood emissions label
- Vehicle-specific repair manual
to identify the correct bank.
Replacing the solenoid on the easier-to-reach side is not a diagnostic strategy, although it has funded an impressive number of unnecessary parts purchases.
What Is an Exhaust Valve Control Solenoid?
The exhaust 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:
- Exhaust VVT solenoid
- Exhaust oil control valve
- Exhaust camshaft actuator solenoid
- Exhaust valve timing control solenoid
- Variable cam timing solenoid
- VCT solenoid
- CVVT oil control valve
- Camshaft position actuator solenoid
The solenoid controls pressurized engine oil flowing to the exhaust camshaft actuator or cam phaser.
By changing that oil flow, the PCM can adjust exhaust camshaft timing according to:
- Engine speed
- Engine load
- Throttle position
- Coolant temperature
- Oil temperature
- Vehicle speed
- Requested torque
- Emissions strategy
Exhaust camshaft timing can influence:
- Idle quality
- Low-speed torque
- High-RPM power
- Fuel economy
- Internal exhaust-gas recirculation
- Turbocharger response
- Exhaust emissions
P0079 means the PCM has detected an electrical problem controlling this solenoid—not necessarily a failed camshaft or timing chain.
How Variable Valve Timing Works
A typical variable valve timing system includes:
- Engine oil supply
- Oil passages in the cylinder head
- Exhaust valve control solenoid
- Exhaust camshaft actuator or phaser
- Camshaft position sensor
- Crankshaft position sensor
- PCM control strategy
When the PCM requests a camshaft adjustment:
- It energizes the exhaust valve control solenoid.
- The solenoid redirects oil pressure.
- Oil enters one side of the camshaft actuator.
- The actuator rotates the exhaust camshaft relative to its timing sprocket.
- The camshaft position sensor reports the result.
- The PCM compares desired and actual camshaft timing.
If the electrical circuit remains too low, the PCM may disable variable valve timing and store P0079.
How the Exhaust Valve Control Solenoid Circuit Works
Many exhaust VVT solenoids use two wires.
A common low-side-controlled system includes:
- Battery or ignition voltage on one terminal
- PCM-controlled ground on the other terminal
The PCM controls the solenoid using pulse-width modulation.
Rather than simply switching the solenoid fully on or off, it rapidly switches the circuit to regulate:
- Solenoid current
- Internal spool position
- Oil flow
- Camshaft actuator position
The PCM may monitor:
- Circuit voltage
- Solenoid current
- Coil resistance
- Driver feedback
- Commanded duty cycle
- Actual camshaft response
If the PCM detects the circuit is pulled too close to ground or draws excessive current, it may set P0079.
Some applications define P0079 specifically as a short-to-ground condition in the exhaust valve control solenoid circuit.
What Does “Circuit Low” Mean?
“Circuit low” refers to the electrical voltage or driver feedback, not the oil level or camshaft position.
It does not automatically mean:
- Engine oil is low
- Engine oil pressure is low
- Exhaust valves are opening too little
- Camshaft timing is retarded
- Battery voltage is low
Common circuit-low conditions include:
- Signal wire shorted to ground
- Internally shorted solenoid coil
- Excessive current draw
- Missing supply voltage
- PCM control circuit permanently grounded
- Connector terminals shorted together
- Failed PCM driver
A shorted control circuit may cause the solenoid to remain:
- Fully energized
- De-energized by PCM protection
- Uncontrollable
- Disabled through failsafe logic
The exact result depends on circuit design.
P0078 vs P0079 vs P0080
| Code | Description | Typical Meaning |
| P0078 | Exhaust Valve Control Solenoid Circuit Bank 1 | General circuit malfunction |
| P0079 | Exhaust Valve Control Solenoid Circuit Low Bank 1 | Circuit voltage below specification |
| P0080 | Exhaust Valve Control Solenoid Circuit High Bank 1 | Circuit voltage above specification |
Related Bank 2 exhaust-solenoid codes include:
| Code | Description |
| P0084 | Exhaust Valve Control Solenoid Circuit Bank 2 |
| P0085 | Exhaust Valve Control Solenoid Circuit Low Bank 2 |
| P0086 | Exhaust Valve Control Solenoid Circuit High Bank 2 |
P0079 vs P0013
P0013 is generally defined as:
“B” Camshaft Position Actuator Circuit Bank 1
P0079 is defined as:
Exhaust Valve Control Solenoid Circuit Low Bank 1
Both codes may involve the Bank 1 exhaust camshaft oil-control solenoid.
The difference is that:
- P0013 is a broader exhaust camshaft actuator circuit code.
- P0079 specifically identifies a low circuit condition.
Manufacturer terminology varies, so follow the diagnostic procedure written for the exact code, engine, and model year.
How the PCM Detects P0079
The PCM may set P0079 when:
- Control-circuit voltage stays below its calibrated limit
- Solenoid current is higher than expected
- The control wire is shorted to ground
- The solenoid coil has abnormally low resistance
- Supply voltage is missing or severely reduced
- Circuit feedback does not match the PCM command
- The low condition remains present for a calibrated period
On one documented Hyundai strategy, P0079 is detected through an electrical check when the exhaust valve control solenoid control circuit is shorted to ground. The listed diagnostic time is approximately two seconds under valid battery-voltage conditions, although these details are application-specific.
The PCM may respond by:
- Illuminating the Check Engine Light
- Disabling exhaust variable valve timing
- Storing freeze-frame data
- Entering failsafe mode
- Holding the exhaust camshaft in a default position
Symptoms of P0079
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
Poor acceleration and reduced fuel economy are commonly associated with P0079 because the PCM may disable variable valve timing when it detects the low circuit condition.
The severity depends on:
- Engine design
- Default exhaust camshaft position
- Whether the solenoid remains energized
- Whether the fault is permanent or intermittent
- Whether additional timing codes are present
- Mechanical condition of the cam phaser
Can P0079 Cause a Rough Idle?
Yes.
Incorrect exhaust camshaft timing can affect:
- Exhaust-gas scavenging
- Internal EGR
- Manifold vacuum
- Combustion stability
- Cylinder filling
Possible results include:
- Rough idle
- Surging
- Misfires
- Stalling
- Poor cold-start operation
However, rough idle may also be caused by:
- Vacuum leaks
- Ignition faults
- Fuel-delivery problems
- Low compression
- Mechanical timing errors
- Camshaft position sensor faults
Confirm that the P0079 circuit problem is active before attributing every idle complaint to the exhaust VVT solenoid.
Can P0079 Cause Poor Acceleration?
Yes.
Exhaust camshaft timing contributes to:
- Cylinder scavenging
- Volumetric efficiency
- Turbocharger response
- Torque production
- Emissions control
When exhaust VVT is disabled, the engine may feel:
- Sluggish
- Flat at low RPM
- Weak at higher RPM
- Slow to build boost
- Less responsive to throttle
Poor acceleration is a recognized P0079 symptom.
Common Causes of P0079
1. Exhaust VVT Solenoid Shorted Internally
The solenoid’s internal coil may short between windings.
This can produce:
- Resistance below specification
- Excessive current draw
- Low control-circuit voltage
- Blown fuse
- PCM driver shutdown
- P0079
An internally shorted solenoid is one of the most common direct causes of a circuit-low code.
2. Control Wire Shorted to Ground
The PCM-controlled wire may rub through its insulation and touch:
- Cylinder head
- Valve cover
- Engine bracket
- Intake manifold support
- Exhaust heat shield
- Ground wire
- Metal harness retainer
A documented manufacturer-specific P0079 definition identifies a control-circuit short to ground as a primary detection condition.
3. Melted Engine Wiring
The exhaust solenoid is often located near high-temperature components.
Wiring may be damaged by:
- Exhaust manifold heat
- Turbocharger heat
- EGR pipes
- Cylinder-head temperature
- Missing heat shield
- Incorrect harness routing
Melted insulation may allow:
- Wire-to-ground contact
- Wire-to-wire shorts
- Intermittent circuit failure
- Excessive current
4. Chafed Wiring Harness
The wiring may rub against:
- Valve-cover edge
- Cam-cover bracket
- Cylinder-head casting
- Engine lifting bracket
- Wiring tray
- Metal clip
Engine vibration can gradually wear through the insulation.
The harness does not need to look dramatically destroyed. One exposed copper strand touching the cylinder head is enough to create an electrical shortcut.
5. Failed Exhaust Valve Control Solenoid
The solenoid may fail because of:
- Electrical coil damage
- Heat
- Age
- Vibration
- Oil contamination
- Internal corrosion
- Manufacturing defect
Electrical testing may reveal:
- Resistance below specification
- Short to housing
- Excessive current draw
- No controlled response
6. Corroded Connector Terminals
Corrosion can create:
- Voltage loss
- Unstable current
- Terminal bridging
- Poor PCM feedback
- Intermittent low circuit
Inspect for:
- Green deposits
- White oxidation
- Darkened terminals
- Moisture
- Oil
- Damaged seals
- Loose pins
Poor connectors and wiring problems are recognized common P0079 causes.
7. Oil-Contaminated Connector
Oil may enter the connector because of:
- Solenoid seal failure
- Valve-cover leak
- Oil migration through the solenoid
- Harness contamination
Oil can:
- Trap debris
- Damage seals
- Reduce terminal contact
- Wick through wiring
- Contribute to intermittent electrical behavior
Repair the source of the leak rather than cleaning the connector and sending it back into the same oil bath.
8. Water Intrusion
Water may enter through:
- Damaged connector seal
- Broken connector housing
- Unsealed wiring repair
- Pressure washing
- Coolant leak near the harness
Moisture may bridge the terminals and create a low-resistance path to ground.
9. Connector Terminals Shorted Together
Bent terminals, moisture, metal debris, or damaged insulation may connect:
- Power to control
- Control to ground
- Adjacent actuator circuits
Inspect terminal spacing and connector condition carefully.
10. Incorrectly Wired Replacement Pigtail
A replacement connector may have:
- Reversed wires
- Terminals installed in wrong cavities
- Poor crimps
- Wrong connector body
- Unsealed splices
Verify the pinout using the wiring diagram.
Matching colors is not enough when the replacement pigtail manufacturer selected different colors—or when the previous technician treated wire identification as a creative exercise.
11. Missing Solenoid Power Supply
Depending on circuit design, missing supply voltage may create a low monitored value.
Possible causes include:
- Blown fuse
- Failed relay
- Open power wire
- Corroded splice
- Loose fuse-box terminal
- PCM power-distribution fault
If several VVT or actuator codes appear together, inspect shared power supplies before replacing multiple solenoids.
12. Blown Fuse
A fuse may blow because of:
- Shorted solenoid coil
- Power wire shorted to ground
- Melted harness
- Another actuator on the shared circuit
- Incorrect electrical repair
Do not repeatedly replace a blown fuse.
A fuse does not fail from boredom. It is usually reacting to excessive current somewhere downstream.
13. Failed Engine-Control Relay
A damaged relay may cause:
- Missing voltage
- Intermittent power
- Voltage drop
- Multiple actuator codes
Inspect the relay if it supplies:
- VVT solenoids
- Fuel injectors
- Ignition coils
- Other PCM-controlled actuators
14. High Resistance in the Power Circuit
A circuit may show voltage on a multimeter but collapse under load because of:
- Corroded splice
- Weak relay contact
- Partially broken wire
- Heat-damaged terminal
- Poor previous repair
A voltage-drop or loaded-circuit test is more useful than an unloaded continuity check.
15. Poor PCM or Engine Ground
A poor ground may interfere with:
- PCM driver control
- Circuit monitoring
- Solenoid current
- Sensor feedback
Inspect:
- Battery negative terminal
- Engine ground strap
- Body ground
- PCM ground circuits
- Ground eyelets
Multiple unrelated circuit-low codes make a shared ground problem more likely.
16. Low Battery or Charging Voltage
A weak battery or charging fault may contribute to abnormal actuator operation.
Check:
- Battery state of charge
- Cranking voltage
- Alternator output
- Battery terminals
- Engine grounds
- Body grounds
Low system voltage is less likely when P0079 is the only code, but it should be considered when several circuit-low codes appear together.
17. Low Engine Oil Level
Low oil does not usually create the electrical low signal directly.
However, the exhaust VVT system depends on engine oil to move the camshaft actuator.
Low oil may cause:
- Poor camshaft response
- Solenoid sticking
- Cam phaser noise
- Additional timing codes
- Oil-pressure problems
Always check oil level before performing VVT command tests.
18. Dirty or Sludged Engine Oil
Contaminated oil may restrict:
- Solenoid spool movement
- Solenoid filter screen
- Cylinder-head oil passage
- Camshaft actuator movement
Dirty oil may cause timing-performance codes in addition to P0079.
It will not repair a grounded control wire, but it can ensure the VVT system still performs badly after the wiring fault is fixed.
19. Incorrect Oil Viscosity
Oil that is too thick or too thin can cause:
- Slow camshaft response
- Poor cold-start operation
- Low hot-idle oil pressure
- Cam phaser noise
- Additional VVT codes
Use the manufacturer-specified oil viscosity and standard.
20. Clogged Solenoid Screen
Some exhaust VVT solenoids contain a fine oil screen.
The screen may become blocked by:
- Sludge
- Varnish
- Metal particles
- Gasket debris
- Excessive silicone sealant
A clogged screen is primarily a hydraulic performance problem, but contamination may coexist with an electrically failed solenoid.
21. Incorrect Replacement Solenoid
An incorrect solenoid may have:
- Coil resistance below specification
- Different connector pinout
- Incorrect oil passages
- Incompatible operating characteristics
- Poor internal construction
A new part can still be:
- Wrong
- Defective
- Counterfeit
- Incorrectly cataloged
Fresh packaging is not a diagnostic measurement.
22. PCM Software Issue
A calibration problem may cause the PCM to:
- Interpret driver feedback incorrectly
- Command the solenoid incorrectly
- Store P0079 prematurely
- Disable VVT unnecessarily
Check for:
- Technical service bulletins
- Calibration updates
- Reprogramming instructions
- Revised diagnostic procedures
Software problems are less common than wiring, connector, and solenoid faults.
23. Failed PCM Driver
The internal PCM driver may fail because of:
- Shorted solenoid coil
- Control wire shorted to voltage
- Excessive current
- Water intrusion
- Internal electronic damage
Only suspect the PCM after confirming:
- Solenoid resistance
- Supply voltage
- Control-wire isolation
- Connector condition
- PCM powers and grounds
- Correct calibration
Replacing the PCM before testing the two-wire solenoid circuit is an efficient way to turn a grounded wire into a four-figure repair that still does not work.
Is P0079 Serious?
P0079 is generally considered a moderate-severity code.
The engine may continue running, but exhaust camshaft adjustment may be:
- Disabled
- Fixed in a default position
- Incorrectly activated
- Unavailable under load
Possible consequences include:
- Reduced power
- Rough idle
- Poor fuel economy
- Increased emissions
- Hard starting
- Engine stalling
- Failed emissions testing
P0079 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 becomes hot
- Fuse repeatedly blows
- Timing correlation codes are present
Can You Drive With P0079?
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
- Acceleration remains safe
- No severe timing noise is present
- Wiring is not overheating
Avoid continued driving if:
- Oil-pressure warning is illuminated
- Engine stalls
- Power is severely reduced
- Engine rattles
- Fuse repeatedly blows
- Wiring smells burned
- Misfires are severe
- Engine will not start reliably
A disabled VVT system may not immediately damage the engine.
A shorted wire heating against the cylinder head deserves considerably less patience.
How to Diagnose P0079
Step 1: Scan Every Stored Code
Check for:
- P0078
- P0079
- P0080
- P0013
- P0014
- P0015
- P0017
- P0084
- P0085
- P0086
- Camshaft position codes
- Crankshaft position codes
- Misfire codes
- Oil-pressure codes
- System-voltage codes
Record:
- Freeze-frame data
- Pending codes
- Permanent codes
- Engine RPM
- Battery voltage
- Oil temperature
- VVT command
- Desired camshaft angle
- Actual camshaft angle
Multiple circuit-low codes may indicate a shared power or ground problem.
Step 2: Confirm the Code Definition
Verify that the scanner identifies P0079 as:
Exhaust Valve Control Solenoid Circuit Low Bank 1
Do not confuse it with:
- P0078 general circuit fault
- P0080 circuit-high fault
- P0013 exhaust camshaft actuator circuit
- P0014 exhaust timing over-advanced
P0079 is specifically a circuit-low code.
Step 3: Identify Bank 1
Locate:
- Cylinder number 1
- Bank 1 cylinder head
- Bank 1 exhaust camshaft
- Correct exhaust valve control solenoid
Do not confuse:
- Bank 1 with Bank 2
- Intake solenoid with exhaust solenoid
- VVT solenoid with camshaft position sensor
Step 4: Check Engine Oil Level
Park on level ground and check:
- Oil level
- Oil condition
- Correct viscosity
- Signs of leakage
- Oil-pressure warning behavior
Correct low oil before operating the VVT system.
Step 5: Inspect Oil Condition
Look for:
- Sludge
- Varnish
- Fuel dilution
- Coolant contamination
- Metal debris
- Incorrect viscosity
- Excessively long service interval
Perform an oil and filter change if needed, but continue electrical testing because P0079 identifies a circuit-low fault.
Step 6: Locate the Exhaust Valve Control Solenoid
The solenoid may be installed:
- 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 the exhaust camshaft oil passage
Confirm the component using service information.
Step 7: Inspect the Solenoid Connector
Check for:
- Connector not fully seated
- Broken locking tab
- Oil contamination
- Water intrusion
- Bent pins
- Corrosion
- Backed-out terminals
- Spread terminals
- Heat damage
Repair connector problems before replacing the solenoid.
Step 8: Inspect the Wiring Harness
Follow the wiring toward:
- Engine fuse box
- Main engine harness
- PCM
Look for:
- Melted insulation
- Chafing
- Pinched sections
- Contact with exhaust heat
- Contact with metal brackets
- Rodent damage
- Poor splices
- Missing harness clips
Step 9: Check Shared Fuses and Relays
Identify the fuse and relay supplying the exhaust solenoid.
If the fuse is blown:
- Disconnect the solenoid.
- Measure solenoid resistance.
- Check the supply wire for a short.
- Inspect other actuators sharing the fuse.
- Repair the electrical fault.
- Install the correct fuse rating.
- Retest the circuit.
Never install a larger fuse.
That does not increase reliability. It merely allows the wiring harness to audition for the role of the fuse.
Step 10: Measure Solenoid Resistance
Disconnect the solenoid and measure resistance across its terminals.
Compare the result with manufacturer specifications.
Possible findings include:
- Resistance too low: shorted coil
- Near-zero resistance: severe internal short
- Infinite resistance: open coil
- Correct resistance: continue circuit testing
Do not use a generic resistance specification from a different vehicle.
Step 11: Check for a Short to the Solenoid Housing
When permitted by service information, measure resistance between:
- Terminal 1 and solenoid body
- Terminal 2 and solenoid body
Unexpected continuity may indicate an internal short.
Step 12: Disconnect the Solenoid and Observe Circuit Status
With the solenoid unplugged, monitor the circuit using:
- Scan-tool data
- Multimeter
- Manufacturer test procedure
If the low condition changes to high or open:
- The solenoid may be internally shorted
If the circuit remains low with the solenoid unplugged:
- Control wire may be shorted to ground
- Supply voltage may be missing
- Connector may be bridged
- PCM driver may be faulty
Interpret results using the exact circuit design.
Step 13: Verify Supply Voltage
With ignition on, test the solenoid power terminal.
Expected voltage may be:
- Battery voltage
- Ignition voltage
- Relay-controlled voltage
- PCM-controlled voltage
If voltage is missing, inspect:
- Fuse
- Relay
- Power splice
- Supply wire
- Fuse-box terminal
Step 14: Load-Test the Supply Circuit
An unloaded circuit may show normal voltage through a corroded connection.
Perform an approved loaded test to check:
- Fuse terminals
- Relay contacts
- Power wire
- Connector terminals
- Shared splices
A voltage collapse under load indicates excessive resistance.
Step 15: Test the PCM Control Wire for a Short to Ground
Disconnect the PCM and solenoid as instructed.
Measure resistance between:
- Control wire
- Chassis ground
- Engine ground
Unexpected continuity indicates a short-to-ground condition.
Move the harness during testing because the short may occur only when the wire touches a bracket.
Step 16: Check for a Short Between Circuits
Test whether the control circuit is contacting:
- Another VVT circuit
- Injector wiring
- Ignition wiring
- Sensor ground
- Heater circuit
- Solenoid supply wire
Melted harness sections may connect several circuits together.
Step 17: Check Circuit Continuity
Test both wires from the solenoid connector to their destinations.
Inspect for:
- Open circuit
- Excessive resistance
- Incorrect terminal position
- Corroded splice
- Weak previous repair
Circuit resistance should meet manufacturer specifications.
Step 18: Perform Voltage-Drop Tests
With the circuit commanded on, measure voltage drop across:
- Power wire
- Fuse
- Relay
- Connector terminals
- Control circuit
- PCM ground
Excessive voltage drop indicates unwanted resistance.
Step 19: Command the Solenoid With a Scan Tool
Use a bidirectional scan tool when supported.
Monitor:
- Exhaust solenoid command
- Duty cycle
- Control voltage
- Current draw
- Desired exhaust camshaft angle
- Actual exhaust camshaft angle
- Engine idle
Possible results include:
- Excessive current: shorted solenoid or wiring
- Circuit voltage stuck low: short to ground or PCM driver fault
- No supply voltage: fuse, relay, or power-wire fault
- Electrical response but no camshaft movement: hydraulic or mechanical problem
Step 20: Use a Current Clamp
A low-current clamp can help evaluate solenoid operation without opening the circuit.
Possible findings include:
- Excessive current: shorted coil
- Zero current: missing power or open circuit
- Unstable current: loose connection
- Current present when command is off: grounded control wire
Compare the waveform with:
- Manufacturer data
- Known-good Bank 2 circuit
- Identical known-good vehicle
Step 21: Examine the PWM Signal
An oscilloscope can display:
- Duty cycle
- Voltage amplitude
- PCM switching
- Current ramp
- Driver shutdown
- Electrical noise
A waveform stuck near ground may indicate:
- Grounded control wire
- Internally shorted solenoid
- Failed PCM driver
Step 22: Perform a Wiggle Test
Monitor circuit voltage and current while moving:
- Solenoid connector
- Harness near the valve cover
- Wiring near the exhaust manifold
- Fuse-box connectors
- PCM connector
- Previous repair areas
Watch for:
- Voltage changes
- Current spikes
- Code status changes
- Idle changes
- Camshaft response
Step 23: Inspect the Solenoid Mechanically
If electrical testing passes, remove the solenoid according to the repair procedure.
Inspect for:
- Sludge
- Varnish
- Metal particles
- Damaged screen
- Stuck spool valve
- Broken O-ring
- Silicone contamination
Mechanical restrictions generally cause performance codes, but they may coexist with P0079.
Step 24: Compare Bank 1 With Bank 2
On engines with two banks, compare:
- Solenoid resistance
- Supply voltage
- Control signal
- Current draw
- Desired timing
- Actual timing
A healthy Bank 2 circuit may provide a valuable reference.
Confirm that both sides use the same component before comparing resistance or swapping parts.
Step 25: Swap Solenoids Only When Approved
If the Bank 1 and Bank 2 exhaust solenoids are identical, a controlled swap may help isolate the fault.
After swapping:
- Code moves to Bank 2: solenoid likely faulty
- P0079 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
- Charging-system voltage
A poor PCM ground can create misleading driver-circuit faults.
Step 27: Check Technical Service Bulletins
Search manufacturer information using:
- VIN
- Model year
- Engine code
- P0079
- Solenoid part number
- PCM calibration number
- Related codes
Possible factory corrections include:
- Updated solenoid
- Revised wiring
- Connector repair
- Harness relocation
- PCM software update
- Revised diagnostic procedure
Step 28: Evaluate the PCM Driver
Only evaluate PCM failure after confirming:
- Solenoid resistance is correct
- Supply voltage is present
- Control wire is not grounded
- Wiring continuity is correct
- Connector terminals are secure
- PCM powers and grounds are correct
- Software is current
If the PCM driver remains grounded or cannot control the circuit after all external tests pass, the PCM may require:
- Software update
- Module repair
- Replacement and programming
Step 29: Verify the Repair
After completing repairs:
- Clear all diagnostic trouble codes.
- Start the engine.
- Confirm the oil-pressure warning light turns off normally.
- Monitor the Bank 1 exhaust solenoid command.
- Check circuit voltage and current.
- Compare desired and actual exhaust camshaft timing.
- Verify normal idle quality.
- Road-test under varied load and RPM.
- Complete the required drive cycle.
- Rescan for pending and confirmed codes.
- Confirm P0079 does not return.
Common Repairs and Costs
| Repair | Estimated Cost |
| Reconnect or reseat connector | $0–100 |
| Clean electrical connector | $50–150 |
| Replace connector terminals | $75–250 |
| Engine oil and filter change | $60–180 |
| Replace exhaust VVT solenoid | $150–500 |
| Repair shorted wiring | $150–650 |
| Replace solenoid connector | $100–325 |
| Replace fuse or relay after repairing fault | $75–250 |
| Repair engine power-supply circuit | $150–700 |
| 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 cost depends on:
- Vehicle design
- Solenoid accessibility
- Wiring location
- Labor rate
- Oil condition
- Whether additional timing faults exist
- Whether module programming is required
A shorted solenoid mounted at the top of the cylinder head may be straightforward.
A grounded control wire buried beneath the intake manifold may require dismantling half the engine bay to reach the automotive equivalent of one bad extension cord.
Common Diagnostic Mistakes
Avoid these common P0079 diagnostic mistakes:
- Calling P0079 an intermittent circuit code
- Assuming P0078 is circuit high
- Assuming “circuit low” means low oil level
- Replacing the solenoid without checking resistance
- Ignoring a blown fuse
- Replacing the fuse without locating the short
- Misidentifying Bank 1
- Confusing intake and exhaust solenoids
- Ignoring melted wiring near the exhaust
- Checking voltage without loading the circuit
- Checking only continuity
- Replacing the cam phaser before testing the electrical circuit
- Replacing the PCM before isolating the control wire
- Installing an incorrect aftermarket solenoid
- Failing to verify the repair with scan-tool commands
P0079 is an electrical circuit-low code.
The timing chain may eventually require service, but replacing it because one wire is touching the cylinder head is an impressively expensive misunderstanding.
Vehicles Commonly Affected
P0079 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:
- Exhaust oil control valve
- Exhaust valve timing control solenoid
- Exhaust VVT solenoid
- VCT solenoid
- Exhaust camshaft actuator solenoid
- CVVT oil control valve
P0079 is particularly documented on Hyundai and Kia applications, where it may indicate the exhaust oil-control-valve circuit is shorted to ground.
P0079 on Hyundai and Kia Vehicles
Hyundai and Kia may refer to the component as the:
- Exhaust oil control valve
- Exhaust CVVT oil control valve
- Exhaust valve control solenoid
On certain applications, the PCM uses pulse-width modulation to control the oil control valve and monitors the circuit for a short to ground.
Common inspection areas include:
- Exhaust solenoid coil resistance
- Solenoid connector
- Wiring near the cylinder head
- Shared actuator power supply
- PCM control wire
- Engine oil level and condition
A documented Hyundai diagnostic reference lists a short to ground, damaged harness, poor connection, or faulty exhaust valve control solenoid among possible P0079 causes.
P0079 on Nissan and Infiniti Vehicles
Nissan and Infiniti may refer to the component as the:
Exhaust Valve Timing Control Solenoid Valve
Possible causes include:
- Shorted solenoid coil
- Harness short to ground
- Corroded connector
- Missing solenoid power
- ECM driver fault
- Incorrect replacement component
Check oil condition and pressure if additional exhaust camshaft timing-performance codes are present.
P0079 After Engine Repairs
If P0079 appears after:
- Valve-cover replacement
- Cylinder-head repair
- Timing-chain service
- Engine replacement
- Intake manifold removal
- Solenoid replacement
inspect for:
- Connector attached incorrectly
- Harness pinched beneath a bracket
- Wire trapped under the valve cover
- Ground strap omitted
- Replacement pigtail wired backward
- Incorrect solenoid installed
- 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 may control valve timing thousands of times per minute, but it remains unable to reroute a wire that was crushed during yesterday’s valve-cover job.
P0079 After a Blown Fuse
If the actuator or engine-control fuse is blown:
- Disconnect the Bank 1 exhaust VVT solenoid.
- Measure solenoid resistance.
- Test the power wire for a short to ground.
- Inspect other actuators sharing the fuse.
- Check wiring near hot and moving components.
- Repair the fault.
- Install the correct fuse.
- Monitor current while commanding the circuit.
Never substitute a higher-amperage fuse.
The original fuse was attempting to protect the harness. Overruling it does not improve the diagnosis.
Can Dirty Oil Cause P0079?
Dirty oil may contribute to VVT performance problems, but P0079 specifically indicates a low electrical circuit condition.
Dirty oil may cause:
- Solenoid spool sticking
- Restricted screen
- Slow camshaft response
- Cam phaser noise
- P0014 or P0015
It generally does not directly cause:
- Control wire shorted to ground
- Shorted electrical coil
- Blown actuator fuse
- Missing supply voltage
Check oil condition, but do not abandon electrical testing because the oil is dark.
Can a Bad VVT Solenoid Cause P0079?
Yes.
A failed exhaust VVT solenoid can cause P0079 if its internal coil:
- Shorts between windings
- Draws excessive current
- Has resistance below specification
- Shorts to the housing
- Fails electrically when hot
Measure resistance and current rather than replacing the solenoid solely because its name appears in the code.
Can a Bad Camshaft Position Sensor Cause P0079?
A camshaft position sensor is not a common direct cause of P0079.
The camshaft sensor reports camshaft position, while P0079 monitors the exhaust valve control solenoid circuit.
A failed camshaft sensor is more likely to set:
- Camshaft sensor code
- Timing correlation code
- VVT performance code
- Starting or stalling complaint
Diagnose all stored codes together.
How to Prevent P0079
Reduce the likelihood of P0079 by:
- Maintaining the correct engine-oil 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 clips
- Keeping wiring away from exhaust heat
- Inspecting wiring after engine repairs
- Using OEM-quality VVT solenoids
- Avoiding oversized electrical test probes
- Repairing blown-fuse causes immediately
Frequently Asked Questions
What does P0079 mean?
P0079 means the PCM has detected a lower-than-expected electrical signal in the Bank 1 exhaust valve control solenoid circuit.
What is the full definition of P0079?
The generic definition is:
Exhaust Valve Control Solenoid Circuit Low Bank 1
Is P0079 an intermittent circuit code?
No.
P0079 is normally the circuit-low code.
The sequence is:
- P0078: general circuit fault
- P0079: circuit low
- P0080: circuit high
Where is Bank 1?
Bank 1 is the side of the engine containing cylinder number 1.
Inline engines have only one bank, which is Bank 1.
What does circuit low mean?
Circuit low means the monitored voltage or driver feedback is below the PCM’s expected range.
It commonly indicates:
- Short to ground
- Shorted solenoid coil
- Missing supply voltage
- Failed PCM driver
Does circuit low mean the engine oil is low?
No.
The word “low” refers to the electrical circuit.
Low oil may cause related VVT performance problems but is not the same condition.
What causes P0079 most often?
Common causes include:
- Shorted exhaust VVT solenoid
- Control wire shorted to ground
- Damaged wiring
- Corroded connector
- Blown fuse
- Missing power supply
- PCM driver fault
Is P0079 serious?
P0079 is moderately serious.
The vehicle may remain drivable, but engine performance, fuel economy, idle quality, and emissions may suffer.
Can I drive with P0079?
Possibly for a short distance if:
- Oil pressure is normal
- Engine runs smoothly
- No severe noise is present
- Wiring is not overheating
Stop driving if the oil-pressure warning appears, the engine rattles, it stalls, or power loss becomes severe.
Can P0079 cause rough idle?
Yes.
Incorrect exhaust camshaft timing may create rough idle, surging, misfires, or stalling.
Can P0079 cause poor acceleration?
Yes.
Loss of exhaust camshaft control can reduce torque, throttle response, and turbocharger performance.
Can P0079 blow a fuse?
Yes.
An internally shorted solenoid or grounded supply wire may blow a shared actuator fuse.
Can dirty oil cause P0079?
Dirty oil can create hydraulic VVT problems, but P0079 requires electrical testing because it identifies a circuit-low condition.
What is the difference between P0078 and P0079?
P0078 indicates a general Bank 1 exhaust valve control solenoid circuit malfunction.
P0079 specifically indicates a low circuit condition.
What is the difference between P0079 and P0080?
P0079 indicates circuit voltage below specification.
P0080 indicates circuit voltage above specification.
Can I test the solenoid with a multimeter?
Yes.
Common tests include:
- Coil resistance
- Short to housing
- Supply voltage
- Control-wire short to ground
- Circuit continuity
- Voltage drop
Use vehicle-specific specifications.
Can I apply battery voltage directly to the solenoid?
Only when the manufacturer’s procedure permits it.
Incorrect polarity, excessive voltage, or continuous power may damage the solenoid or PCM circuit.
Does a new exhaust VVT solenoid require programming?
Usually not.
The vehicle may require:
- Code clearing
- Drive cycle
- Camshaft relearn
- Oil service reset
- PCM adaptation
A replacement PCM requires programming.
How much does P0079 cost to repair?
A typical exhaust VVT solenoid replacement costs approximately $150–500.
Wiring, fuse-box, camshaft actuator, timing-chain, or PCM repairs may cost substantially more.
Final Thoughts
The P0079 code means the PCM has detected a low electrical condition in the Bank 1 exhaust valve control solenoid circuit.
The most common causes include:
- Internally shorted exhaust VVT solenoid
- PCM control wire shorted to ground
- Melted or chafed engine wiring
- Corroded connector terminals
- Missing supply voltage
- Blown fuse
- Failed relay
- PCM driver fault
Start diagnosis by:
- Confirming P0079 is the circuit-low code.
- Scanning for related codes.
- Identifying Bank 1 correctly.
- Checking oil level and condition.
- Inspecting the exhaust solenoid connector.
- Examining the harness for grounded wiring.
- Measuring solenoid resistance.
- Checking the fuse and relay.
- Verifying supply voltage.
- Testing the PCM control circuit for a short to ground.
- Commanding the solenoid with a bidirectional scan tool.
Do not interpret “circuit low” as proof that the engine simply needs more oil.
The engine does need the correct oil, but P0079 is warning that the electrical side of the Bank 1 exhaust VVT system has fallen below specification.
The eventual repair may be a shorted solenoid, damaged connector, blown fuse, failed relay, grounded wire, or PCM driver problem.
Variable valve timing may involve hydraulic actuators, computer-controlled duty cycles, camshaft feedback, and enough technical vocabulary to sound expensive.
Sometimes, however, the entire system stops working because one wire rubbed against a metal bracket until it discovered ground.
Related Articles
Related Camshaft Timing Codes
- P0013 Code Explained: “B” Camshaft Position Actuator Circuit Bank 1
- P0014 Code Explained: “B” Camshaft Timing Over-Advanced Bank 1
- P0015 Code Explained: “B” Camshaft Timing Over-Retarded Bank 1
- P0017 Code Explained: Crankshaft–Camshaft Correlation Bank 1 Sensor B
Previous P-Code Articles
- P0076 Code Explained: Intake Valve Control Solenoid Circuit Low Bank 1
- P0077 Code Explained: Intake Valve Control Solenoid Circuit High Bank 1
- P0078 Code Explained: Exhaust Valve Control Solenoid Circuit Bank 1
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