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DTC codes / P03xx · Ignition system and misfire / P0390

P0390Camshaft Position Sensor 'B' Circuit (Bank 2)

P0390 means the engine computer has detected an abnormal signal on the camshaft position sensor 'B' circuit for bank 2, which is the side of the engine that does not contain cylinder number one. The computer monitors the sensor's electrical circuit for expected voltage changes as the camshaft rotates, and it sets this code when the signal is missing, erratic, or out of range.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaIgnition system and misfire

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • Rough idle or misfire, especially when the engine is cold or under light load
  • Hesitation or stumble during acceleration as the computer loses camshaft timing information
  • Reduced fuel economy because the engine management system reverts to a default timing strategy
  • Hard starting or extended cranking before the engine fires, particularly on engines with variable valve timing
  • In some vehicles, a limp-home mode that limits engine speed or disables certain features

Common causes, most likely first

  1. Faulty camshaft position sensor 'B' on bank 2, often due to internal failure or heat damage
  2. Damaged or corroded wiring harness and connector at the sensor, including chafed wires or pushed-back pins
  3. Oil or debris contamination on the sensor tip or the reluctor wheel on the camshaft, disrupting the magnetic signal
  4. Failed reluctor wheel or tone ring on the camshaft, such as a cracked or missing tooth
  5. Poor electrical connection at the engine control module (ECM) or a fault in the sensor's ground circuit
  6. Mechanical timing issues, such as a stretched timing chain or incorrectly installed camshaft, causing the sensor signal to be out of phase
  7. Interference from a failing ignition component or aftermarket accessory wired too close to the sensor circuit

How to diagnose and fix it

  1. Scan all modules for stored and pending codes, then record freeze-frame data to understand when the fault occurs
  2. Visually inspect the sensor, connector, and wiring for damage, corrosion, or oil intrusion, and check for technical service bulletins (TSBs) for your vehicle
  3. Measure the sensor's reference voltage and ground at the connector with a multimeter, and check for signal activity with a lab scope if available
  4. Remove the sensor and inspect the tip and reluctor wheel for metal shavings, sludge, or mechanical damage, cleaning as needed
  5. Perform a resistance and continuity test on the sensor and its wiring between the sensor and the ECM, repairing any open or shorted circuits
  6. Swap the bank 2 sensor with a known-good sensor of the same part number, if accessible, to see if the code moves
  7. If the circuit and sensor test good, verify camshaft timing and reluctor wheel condition before condemning the ECM

What a P0390 rarely tells you

  • A P0390 is often set by a dirty or contaminated sensor tip rather than a failed sensor, so cleaning the sensor and reluctor wheel can resolve the code without parts replacement.
  • On engines with variable valve timing, a stretched timing chain or a faulty camshaft phaser can cause the camshaft position sensor signal to fall outside the expected range, setting P0390 even when the sensor itself is fine.
  • The bank 2 designation can confuse technicians on V6 engines with a single camshaft sensor per bank, so always confirm which bank the scan tool identifies as bank 2 before ordering parts.
  • A weak battery or poor ground can cause intermittent camshaft sensor codes, so check the charging system and engine grounds before replacing the sensor.
  • Aftermarket sensors are a common source of repeat failures; if replacement is needed, use an OEM-quality part to avoid a quick return of the code.

Can I keep driving with P0390?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration, towing, or long trips because the engine may enter limp mode or stall unexpectedly. If the engine runs rough or loses power, stop driving and have it towed to prevent damage to the catalytic converter or other components.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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