P0390 Code: Camshaft Position Sensor “B” Circuit Malfunction Bank 2

The P0390 OBD-II trouble code means the powertrain control module has detected a general electrical malfunction in the Camshaft Position Sensor “B” circuit on Bank 2.

On most dual-overhead-cam engines, Sensor B commonly monitors the exhaust camshaft. However, manufacturers do not all use the same naming convention. Confirm the Sensor B designation through factory service information before ordering parts or dismantling the wrong side of the engine.

Bank 2 is the cylinder bank that does not contain cylinder number one. P0390 therefore does not apply to every engine. An inline four-cylinder engine has only one cylinder bank and normally will not use a Bank 2 code.

A failed camshaft-position sensor can cause P0390, but the code can also result from missing reference voltage, a poor sensor ground, an open signal wire, connector contamination, a damaged reluctor or a PCM input problem. The sensor’s name appears in the code definition. That is a diagnostic clue, not a signed confession.

P0390 Quick Reference

Item	Details
Trouble code	P0390
Code definition	Camshaft Position Sensor “B” Circuit Malfunction Bank 2
System affected	Bank 2 camshaft-position monitoring
Likely sensor	Usually the Bank 2 exhaust camshaft sensor
Fault type	General circuit malfunction or unusable Sensor B signal
Common causes	Failed sensor, damaged wiring, poor connection, missing power or ground
Common symptoms	Check Engine Light, hard starting, rough running, stalling or reduced power
Typical severity	Moderate
Safe to drive?	Possibly for a short distance if the engine runs normally
Repair difficulty	Intermediate electrical diagnosis

What Does the P0390 Code Mean?

P0390 indicates that the PCM cannot detect a valid signal from Camshaft Position Sensor B on Bank 2 or has detected a general malfunction in that circuit.

The camshaft-position signal allows the PCM to determine:

Which cylinder is approaching its compression stroke
Camshaft position relative to the crankshaft
Sequential fuel-injection timing
Ignition timing
Variable-valve-timing operation
Engine synchronization during startup
Misfire-monitoring accuracy

The PCM normally compares the Bank 2 Sensor B waveform with the crankshaft-position signal and other camshaft sensors. If the electrical circuit becomes open, shorted or otherwise unusable, the PCM may store P0390.

P0390 is a general circuit-malfunction code. It does not specify whether the signal is consistently low, consistently high, intermittent or merely outside its expected performance range. Those conditions are covered by the remaining P0390-family codes:

P0391: Sensor B Circuit Range/Performance Bank 2
P0392: Sensor B Circuit Low Input Bank 2
P0393: Sensor B Circuit High Input Bank 2
P0394: Sensor B Circuit Intermittent Bank 2

Use the complete P-series OBD-II code guide to identify additional powertrain faults.

What Does Sensor B Mean?

On many dual-overhead-cam engines:

Sensor A monitors the intake camshaft
Sensor B monitors the exhaust camshaft

That pattern is common, but it is not universal. Some manufacturers define sensors by location, signal function or connector designation instead.

Always verify:

Whether Sensor B is intake or exhaust
Its exact physical location
Connector pinout
Sensor type
Expected waveform
Power and ground requirements

Replacing the intake sensor because it is easier to reach will not repair an exhaust-sensor circuit, although it will provide valuable practice removing a perfectly functional component.

What Does Bank 2 Mean?

Bank 2 is the side of a V-type, flat or opposed engine that does not contain cylinder number one.

Bank 2 is not universally:

The driver side
The passenger side
The front bank
The rear bank
The left side
The right side

The location changes by engine family and vehicle layout.

Use the firing order, cylinder-identification diagram or manufacturer service information to identify Bank 2 correctly.

How the Camshaft-Position Sensor Works

A camshaft-position sensor monitors a toothed, slotted or magnetized trigger wheel attached to the camshaft or camshaft actuator.

As the camshaft rotates, the sensor produces an electrical waveform. The PCM compares that waveform with the crankshaft-position signal to determine which stroke each cylinder is completing.

Two common sensor designs are used.

Hall-Effect Camshaft Sensor

A Hall-effect camshaft sensor commonly has three circuits:

Power or reference voltage
Sensor ground
Digital signal output

The sensor switches its signal between specified high and low voltage levels as the trigger wheel rotates.

A Hall-effect Sensor B may stop producing a valid waveform because of:

Missing reference voltage
Open ground
Signal shorted to ground
Signal shorted to voltage
Internal sensor failure
Open signal wire
Damaged trigger wheel

Magnetic Camshaft Sensor

A magnetic or variable-reluctance sensor typically uses two wires and generates an alternating-current waveform.

Its output depends on:

Camshaft speed
Sensor air gap
Sensor magnet strength
Trigger-wheel condition
Circuit resistance
Temperature

The correct test procedure depends on the sensor design. Do not apply three-wire Hall-effect voltage tests to a two-wire magnetic pickup.

Symptoms of a P0390 Code

Possible symptoms include:

Illuminated Check Engine Light
Extended cranking
Hard starting
Engine cranks but does not start
Rough idle
Engine hesitation
Reduced power
Poor throttle response
Engine stalling
Misfire-like operation
Increased fuel consumption
Limp-home mode
Variable-valve-timing system disabled
Difficult hot or cold starting
No noticeable symptoms beyond the warning light

Some engines can start and run using the crankshaft-position sensor and other camshaft inputs. The PCM may disable variable valve timing or switch to a backup injection strategy.

If the engine turns over normally but does not start, use the engine cranks but won’t start diagnostic guide to check spark, fuel pressure, injector operation and synchronization data.

If the engine shuts off after reaching operating temperature, review why an engine stalls when warm.

Common Causes of P0390

Potential causes include:

Failed Bank 2 Camshaft Position Sensor BInternal electronics, windings or magnetic elements may fail because of heat, age or vibration.
Open Sensor Signal WireA broken signal conductor can prevent the waveform from reaching the PCM.
Signal Circuit Shorted to GroundDamaged insulation may allow the signal wire to contact the cylinder head, engine block or chassis.
Signal Circuit Shorted to VoltageThe signal wire may contact a reference-voltage, ignition-voltage or battery-voltage circuit.
Missing Reference VoltageA Hall-effect sensor cannot operate without its specified power supply.
Poor Sensor GroundCorrosion, loose terminals or high resistance can prevent the sensor from producing a valid signal.
Damaged Sensor ConnectorBroken locks, bent pins or loose terminals can interrupt the circuit.
Oil or Water IntrusionEngine oil may enter the connector through a leaking sensor seal. Moisture can also corrode terminals or bridge adjacent circuits.
Damaged Wiring Near the Cylinder HeadHeat, vibration and previous engine repairs may damage the Sensor B harness.
Incorrect Replacement SensorA sensor with the wrong electrical characteristics or mounting depth may not generate the expected signal.
Improper Sensor InstallationDebris beneath the mounting surface or an improperly seated sensor may affect the air gap.
Damaged Camshaft ReluctorA loose, bent or damaged trigger wheel can prevent the sensor from producing a recognizable waveform.
Camshaft Actuator or Phaser DamageA physically damaged actuator may affect the trigger relationship, although this more commonly produces range/performance or correlation codes.
PCM Connector ProblemCorroded, loose or pushed-back PCM terminals may interrupt the Sensor B input.
PCM Input-Circuit FailureAn internal PCM fault is possible but considerably less common than a sensor, wiring or connector problem.

How Serious Is P0390?

P0390 is usually a moderate-severity fault.

The vehicle may continue running because the PCM can estimate camshaft position from other sensors. However, the engine may experience:

Longer cranking time
Reduced power
Poor fuel economy
Unstable idle
Disabled variable valve timing
Intermittent stalling
A no-start condition

A vehicle that runs normally may be driven a short distance for diagnosis, but continued use is not recommended if the engine stalls, misfires heavily or becomes difficult to restart.

P0390 vs. P0345

P0390 and P0345 both apply to Bank 2 but monitor different camshaft-position inputs.

Code	Sensor	Bank	Fault
P0345	Camshaft Position Sensor A	2	General circuit malfunction
P0390	Camshaft Position Sensor B	2	General circuit malfunction

On many DOHC engines, P0345 applies to the Bank 2 intake camshaft sensor, while P0390 applies to the Bank 2 exhaust camshaft sensor.

Confirm the manufacturer’s definitions before diagnosis.

P0390 vs. the P0365 Family

The P0365 family applies to Camshaft Position Sensor B on Bank 1. P0390 applies to Sensor B on Bank 2.

Existing Bank 1 Sensor B pages include:

Bank identification matters. Repairing the Bank 1 sensor will not correct a Bank 2 circuit fault unless both banks share the actual failed power, ground or reference circuit.

P0390 vs. P0391 Through P0394

The P0390 family divides Bank 2 Sensor B faults by electrical condition.

Code	Definition	Diagnostic focus
P0390	Sensor B Circuit Malfunction Bank 2	General circuit failure or unusable signal
P0391	Sensor B Circuit Range/Performance Bank 2	Signal exists but is implausible
P0392	Sensor B Circuit Low Input Bank 2	Signal voltage remains too low
P0393	Sensor B Circuit High Input Bank 2	Signal voltage remains too high
P0394	Sensor B Circuit Intermittent Bank 2	Signal temporarily drops out

If P0390 appears with one of the more specific codes, begin with the specific voltage, performance or intermittent condition.

How to Diagnose the P0390 Code

P0390 diagnosis should begin with code data and circuit identification. Replacing all four camshaft sensors because the scanner used the word “camshaft” is less diagnosis and more expensive interpretive dance.

1. Confirm P0390

Connect a capable OBD-II scan tool and record:

P0390
Current, pending and history codes
Freeze-frame information
Engine RPM
Battery voltage
Engine coolant temperature
Vehicle speed
Engine load
Camshaft desired and actual positions
Camshaft synchronization
Crankshaft synchronization
Variable-valve-timing command data

Do not erase the code before recording its operating conditions.

2. Check for Related Codes

Look for codes involving:

Bank 2 Sensor A
Bank 2 Sensor B
Bank 1 Sensor B
Crankshaft-position sensors
Camshaft-to-crankshaft correlation
Variable valve timing
Sensor reference voltage
System voltage
PCM communication
Engine misfires

Multiple camshaft sensors failing simultaneously may indicate a shared power, ground or reference-voltage problem.

3. Identify Bank 2 and Sensor B

Use factory service information to confirm:

Cylinder number-one location
Bank 2 location
Whether Sensor B monitors the intake or exhaust camshaft
Sensor connector pinout
Sensor type
Expected supply voltage
Ground circuit
Expected waveform
PCM terminal locations

Do not rely solely on a generic engine diagram or replacement-parts listing.

4. Inspect the Sensor and Connector

Switch the ignition off and inspect:

Sensor housing
Mounting bolt
Connector lock
Terminal tension
Bent or pushed-back pins
Oil contamination
Water intrusion
Corrosion
Damaged connector seals
Wiring near the valve cover and exhaust

Oil inside the electrical connector may indicate a leaking sensor seal. Clean the connector and determine whether the sensor is allowing oil to enter internally.

5. Inspect the Wiring Harness

Follow the Sensor B wiring toward the PCM.

Look for:

Harness contact with exhaust components
Wiring pinched beneath covers or brackets
Stretched wires
Brittle insulation
Improper splices
Melted loom
Oil-soaked wiring
Damage from previous timing or valve-cover repairs
Harness contact with moving components

Pay particular attention to areas where the harness bends sharply near the cylinder head.

6. Check Battery and Charging Voltage

Verify:

Battery state of charge
Minimum cranking voltage
Battery-cable voltage drop
Engine-ground voltage drop
Charging voltage
Alternator ripple

Low cranking voltage can disrupt PCM synchronization and weaken magnetic-sensor output. Correct major voltage problems before interpreting the camshaft waveform.

7. Determine the Sensor Type

Identify whether Sensor B is:

Hall-effect
Magnetoresistive
Magnetic or variable reluctance
Another manufacturer-specific active sensor

The number of wires can provide a clue, but the wiring diagram should make the final determination.

8. Test Hall-Effect Sensor Power

For a three-wire Hall-effect sensor, switch the ignition on and verify the specified supply voltage.

The circuit may use:

Five volts
Eight volts
Battery voltage
Another regulated supply

If power is missing:

Disconnect the sensor.
Recheck the supply circuit.
Inspect for a short to ground.
Check other sensors sharing the supply.
Test continuity to the PCM.
Verify PCM powers and grounds.

If the reference voltage returns when Sensor B is disconnected, the sensor may be internally shorted.

9. Test Sensor Ground

Perform a voltage-drop test on the sensor ground while the circuit is operating.

A simple continuity beep may pass through excessive resistance and falsely approve the circuit.

Inspect:

Ground terminals
Shared ground splices
Cylinder-head grounds
Engine-to-body ground straps
PCM ground circuits

Repair any ground with excessive voltage drop.

10. Check the Signal Circuit

Back-probe the signal wire using a high-impedance digital multimeter or oscilloscope.

During cranking or engine operation, a Hall-effect sensor should switch between its specified high and low states.

A P0390 condition may show:

Completely flat signal
Signal stuck high
Signal stuck low
Missing pulses
No switching despite correct power and ground
Correct signal at the sensor but no signal at the PCM

A multimeter may average the switching voltage. Use an oscilloscope whenever possible.

11. Test a Magnetic Sensor

For a magnetic Sensor B:

Measure resistance only when a specification is provided
Check both circuits for shorts to ground
Measure AC voltage during cranking
Inspect waveform amplitude
Compare hot and cold output
Check for metal debris
Verify the sensor air gap

Resistance alone cannot confirm that a sensor produces a usable waveform.

12. Compare Bank 1 and Bank 2 Signals

Use a multi-channel oscilloscope to compare:

Bank 1 Sensor B
Bank 2 Sensor B
Crankshaft-position signal

If Bank 1 remains stable while Bank 2 is missing, concentrate on the Bank 2 sensor and circuit.

If both Bank 1 and Bank 2 Sensor B signals disappear together, investigate shared:

Power
Ground
PCM operation
Reference voltage

13. Compare the Signal at the Sensor and PCM

Measure the waveform directly at Sensor B and then at the PCM connector.

Possible findings include:

No signal at either location: sensor, power, ground or trigger problem
Signal at the sensor but not PCM: open or shorted wiring
Good signal at PCM but incorrect scan data: PCM input, software or connector problem
Signal changes when the connector moves: terminal or wiring fault

This comparison prevents replacing a sensor when the waveform is being lost elsewhere in the harness.

14. Test Circuit Continuity

Disconnect the sensor and PCM according to service information.

Test the Bank 2 Sensor B circuits for:

End-to-end continuity
Excessive resistance
Short to ground
Short to voltage
Short to another sensor circuit
Intermittent open during harness movement

Never measure resistance on a powered circuit.

15. Inspect the Sensor Air Gap and Reluctor

If power, ground and wiring are correct, inspect:

Sensor mounting
Sensor air gap
Debris under the mounting flange
Trigger-wheel condition
Camshaft reluctor damage
Loose reluctor components
Incorrect replacement sensor length

A damaged or missing trigger can prevent the sensor from producing a waveform even when its electrical circuits are intact.

16. Evaluate Mechanical Timing Only When Supported

P0390 is primarily a circuit-malfunction code. Do not begin with timing-chain replacement.

Investigate mechanical timing when:

The Sensor B waveform is electrically present
Crank-to-cam correlation is incorrect
Timing or variable-valve-timing codes accompany P0390
The engine has abnormal mechanical noise
Recent timing-system repairs were performed
Desired and actual camshaft positions disagree

A stretched chain or failed phaser more commonly produces performance or correlation codes than a basic circuit-malfunction code.

17. Test for Heat-Related Failure

If the fault appears when the engine is hot:

Monitor the waveform during warm-up
Compare cold and hot operation
Move the connector carefully
Apply controlled heat according to service procedures
Cool the sensor and repeat the test

A sensor may fail internally as it heats and recover after cooling.

18. Check the PCM Last

Consider PCM failure only after confirming:

Correct Bank 2 identification
Correct Sensor B identification
Proper sensor power and ground
Good circuit continuity
No short to voltage or ground
Correct sensor installation
Good trigger-wheel condition
Valid waveform reaching the PCM
No applicable software update or technical service bulletin

PCM replacement may require programming, security initialization and camshaft or crankshaft relearn procedures.

Common P0390 Diagnostic Mistakes

Avoid these common mistakes:

Replacing the Bank 1 sensor
Confusing Sensor A with Sensor B
Assuming Sensor B always means exhaust without checking
Identifying Bank 2 by driver or passenger side alone
Replacing the sensor without checking power and ground
Ignoring oil inside the connector
Testing the wrong sensor type
Using resistance alone to approve a magnetic sensor
Replacing a camshaft actuator for a basic electrical fault
Replacing timing components before checking the circuit
Failing to compare the signal at the sensor and PCM
Replacing the PCM before isolating the harness

Repairs That May Fix P0390

Possible repairs include:

Replacing Camshaft Position Sensor B on Bank 2
Repairing an open signal wire
Repairing a signal wire shorted to ground
Repairing a signal wire shorted to voltage
Restoring missing sensor supply voltage
Repairing a poor sensor ground
Cleaning oil or corrosion from the connector
Replacing damaged connector terminals
Replacing a broken sensor connector
Repairing damaged harness shielding
Correcting sensor installation or air gap
Installing the correct replacement sensor
Repairing a damaged camshaft reluctor
Updating PCM software
Repairing a PCM connector
Replacing and programming the PCM after confirmed failure

Mechanical timing or camshaft-actuator repairs should only be performed when separate testing proves those components are involved.

Estimated P0390 Repair Costs

Actual costs depend on the vehicle, sensor accessibility and cause.

Repair	Estimated cost
Diagnostic inspection	$100–$250
Connector or minor wiring repair	$100–$400
Camshaft Position Sensor B replacement	$180–$550
Major harness repair	$350–$1,200
Camshaft reluctor or actuator repair	$600–$2,000
Timing-chain repair	$1,000–$4,000
PCM software update	$100–$300
PCM replacement and programming	$800–$2,500

A sensor mounted at the front of the cylinder head may be inexpensive to replace. One buried behind the engine, intake assembly or firewall can require considerably more labor, because engineers occasionally confuse “compact packaging” with “future mechanic hostility.”

Can You Drive With P0390?

You may be able to drive a short distance with P0390 if the engine starts, runs smoothly and does not stall.

However, continued driving is not recommended if the vehicle has:

Intermittent stalling
Extended cranking
Severe hesitation
Reduced power
Heavy misfiring
Abnormal timing-chain noise
A flashing Check Engine Light
Multiple camshaft or crankshaft codes

If the engine stalls or cannot restart, arrange a tow rather than risking a shutdown in traffic.

Review what the Check Engine Light means for additional warning-light guidance.

How to Verify the Repair

After completing the repair:

Reconnect all sensors and modules.
Confirm proper connector engagement.
Secure the harness away from exhaust heat and moving components.
Clear current and pending codes.
Monitor Bank 2 Sensor B during cranking.
Verify stable camshaft and crankshaft synchronization.
Compare Bank 1 and Bank 2 Sensor B waveforms.
Warm the engine fully.
Recreate the original freeze-frame conditions.
Complete the required drive cycle.
Perform any manufacturer-specified relearn.
Recheck for pending codes.

The repair is confirmed when the Bank 2 Sensor B signal remains stable, synchronization is maintained and P0390 does not return.

Frequently Asked Questions

What does the P0390 code mean?

P0390 means the PCM detected a general electrical malfunction in the Camshaft Position Sensor B circuit on Bank 2.

Is Sensor B the exhaust camshaft sensor?

Sensor B commonly identifies the exhaust camshaft sensor on a DOHC engine, but the manufacturer’s service information must confirm it.

Which side of the engine is Bank 2?

Bank 2 is the cylinder bank that does not contain cylinder number one. Its physical side varies by engine.

Does P0390 mean the camshaft sensor is bad?

Not necessarily. The sensor may have failed, but missing power, poor ground, damaged wiring, connector contamination or a PCM input problem can cause the same code.

Can P0390 cause a no-start condition?

Yes. Some engines may not start if the PCM cannot establish camshaft and crankshaft synchronization.

Can low oil cause P0390?

Low or contaminated oil can affect variable-valve-timing operation, but P0390 is primarily an electrical circuit code. Oil problems are more likely to produce timing, performance or correlation codes.

What is the difference between P0345 and P0390?

P0345 applies to Camshaft Position Sensor A on Bank 2. P0390 applies to Camshaft Position Sensor B on Bank 2.

What is the difference between P0365 and P0390?

P0365 applies to Sensor B on Bank 1. P0390 applies to Sensor B on Bank 2.

Can a damaged reluctor cause P0390?

Yes. A damaged or missing trigger can prevent the sensor from producing a usable waveform even when its electrical circuits are intact.

How do you diagnose P0390?

Identify Bank 2 and Sensor B, verify sensor power and ground, inspect the waveform and compare it at the sensor and PCM.

Final Thoughts

P0390 identifies a malfunction in the Bank 2 Camshaft Position Sensor B circuit. On many DOHC engines, that means the Bank 2 exhaust camshaft sensor, but service information should confirm the designation.

Start by identifying the correct bank and sensor. Then inspect the connector, verify power and ground and measure the signal waveform. Comparing the Bank 2 Sensor B signal with Bank 1 and the crankshaft-position waveform can quickly separate a sensor or wiring failure from a broader synchronization problem.

Replacing a sensor may ultimately be the correct repair. Proving that the sensor failed before buying it remains the cheaper and considerably less theatrical approach.

Visit the OBD-II Doctor for additional diagnostic guides or browse the complete P-series OBD-II code reference to identify related powertrain faults.