P0256 indicates a malfunction in the fuel metering control circuit for Injector Bank B, camshaft‑rotor (cam‑rotor) control. The PCM detects an abnormal voltage or signal from the cam‑rotor position sensor or its circuit.
The sensor that monitors camshaft position for Bank B can fail electrically or mechanically, causing an out‑of‑range signal.
Corroded pins, broken wires, or high resistance in the harness can produce erratic sensor signals.
Excessive wear, a slipped timing chain/belt, or an incorrectly installed cam‑rotor can cause the sensor to read values outside the expected range.
A malfunction in the PCM’s output driver for Bank B injectors can mimic a sensor fault, though this is less common.
Clearing the code may turn off the light temporarily, but if the underlying fault remains, the code will return and the engine may continue to run poorly.
No. In most cases the problem is the cam‑rotor sensor, its wiring, or timing. PCM failure is rare and should be considered only after all other possibilities are ruled out.
Yes, because the fuel metering control is not operating correctly, the vehicle may not meet emissions standards and will likely fail until the issue is repaired and the monitors are reset.
If voltage and resistance tests are outside specifications, the sensor itself is likely defective and should be replaced.