Faulty camshaft position sensor B on bank 2; Damaged, chafed or corroded wiring or connector to the sensor (open circuit, short or high resistance); Camshaft timing out of position due to a stretched chain, worn tensioner or jumped belt; Damaged or contaminated reluctor or trigger wheel, or oil contamination on the sensor; Weak battery or poor power or earth supply causing an unstable sensor signal; Fault in the variable valve timing system or its actuator affecting camshaft position; Fault in the engine control unit.

P0390

Camshaft Position Sensor B Circuit Bank 2.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
3: AreaIgnition system or misfire
90: FaultThe specific fault in that area

What it means

P0390 is the generic code for a fault in the camshaft position sensor B circuit on bank 2. The engine control unit has detected an implausible, missing or out-of-range signal from that sensor, or the signal does not match the crankshaft position signal. Which camshaft this sensor reads (intake or exhaust) depends on the engine, so check the model's wiring and layout information.

Symptoms

Engine warning light on
Long cranking or hard starting
Rough running or misfiring
Loss of power or poor acceleration
Engine stalling or cutting out intermittently
Car running in limp mode or with poor fuel economy

Possible causes

Faulty camshaft position sensor B on bank 2likely
Damaged, chafed or corroded wiring or connector to the sensor (open circuit, short or high resistance)likely
Camshaft timing out of position due to a stretched chain, worn tensioner or jumped beltpossible
Damaged or contaminated reluctor or trigger wheel, or oil contamination on the sensorpossible
Weak battery or poor power or earth supply causing an unstable sensor signalpossible
Fault in the variable valve timing system or its actuator affecting camshaft positionpossible
Fault in the engine control unitrare

How to diagnose

Read all stored and pending codes and the freeze frame data to see engine speed, load and temperature when the fault set, and note any crankshaft sensor or cam timing codes.
Confirm which sensor is bank 2 sensor B on this engine using model-specific information.
Inspect the sensor, its wiring and connector for oil ingress, chafing, heat damage, corrosion and a loose or broken locking tab.
Check the battery condition and charging voltage, and check the main earths.
Test the sensor's supply, earth and signal wires for continuity, shorts and voltage against the manufacturer's specification.
Check the sensor signal on a scope while cranking and running, comparing it with the crankshaft signal for pattern and timing correlation.
Inspect the trigger wheel for damage and check the cam timing against the manufacturer's marks, including chain stretch if the engine is prone to it.
Check the oil level and condition and the operation of the variable valve timing system if fitted.

How to fix

Replace the camshaft position sensor if it fails electrical or signal testing, and clean the mounting area.
Repair or replace damaged wiring, terminals or connectors, and fix any oil leak that is contaminating the harness.
Correct the valve timing by replacing worn chain, tensioners, guides or belt, and set the timing to specification.
Replace a damaged trigger wheel or reluctor.
Repair the variable valve timing fault found, such as a faulty solenoid or low oil supply, following the manufacturer's procedure.
Restore good power and earth supply by charging or replacing the battery and repairing poor connections.

Can I keep driving?

Medium severity

Short, careful drives may be possible, but the engine can stall, run poorly or lose power without warning, which is a safety risk. Have it checked soon, and stop driving if it runs very roughly or the timing is suspected to be wrong, as engine damage could follow.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.