P0390 indicates the Powertrain Control Module (PCM) has detected a malfunction in the Camshaft Position (CMP) Sensor B circuit for Bank 2. The CMP sensor monitors the camshaft's rotational position and speed, sending this information to the PCM for proper fuel injection and ignition timing. Bank 2 refers to the engine cylinder bank that does not contain cylinder number 1 (on V-type engines) or the secondary camshaft position on inline engines with multiple camshafts.
The most common cause is a defective or worn-out CMP sensor, which can fail due to heat, age, oil contamination, or internal electrical failure.
Damaged, chafed, corroded, or loose wiring and connectors between the CMP sensor and PCM can cause intermittent or complete signal loss.
A跳过 teeth on the timing belt or chain, or a stretched chain, can cause incorrect cam position readings and trigger this code.
A worn or damaged camshaft, excessive end play, or cam sensor ring damage can prevent proper sensor triggering.
On engines with variable valve timing, a faulty oil control valve (OCV) can cause cam timing errors that affect CMP sensor readings.
A defective PCM can cause this code, but this is uncommon and should only be diagnosed after all other causes are ruled out.
It is not recommended to drive long distances with this code. The vehicle may experience hard starting, stalling, or reduced power, leaving you stranded. If the engine runs, drive minimally to a repair facility.
In most cases, only the sensor itself needs replacement. However, the underlying cause of the sensor failure (such as oil contamination, wiring issues, or timing problems) should be addressed to prevent recurrence.
While the PCM can fail, it is rarely the cause of P0390. Many shops or parts retailers may suggest PCM replacement as a first guess or because they lack proper diagnostic equipment. The camshaft position sensor, wiring, and timing components are far more common culprits and should be thoroughly checked first.
The code may clear temporarily after battery disconnection, but it will return once the PCM retests the system if the underlying fault remains. Proper diagnosis and repair is necessary to resolve the issue permanently.