OBD-II code C0618 indicates that the park brake control module has detected a high voltage condition on its control circuit. This typically means the signal wire is shorted to a power source, or a component like the park brake switch or control module is internally faulted, sending an abnormally high voltage to the module's input.
Wiring harness chafing, pinched wires, or insulation damage can cause the signal wire to contact a 12V power source, driving the circuit voltage high.
The switch may be stuck closed or internally shorted, sending a constant high signal to the control module instead of switching states.
Internal electronic failure within the module can cause it to misinterpret circuit voltage or create a high reading on its own input.
Moisture intrusion, bent pins, or corrosion at the park brake switch or control module connector can create a resistive short to a nearby power pin.
If the park brake signal is processed by the BCM or cluster, an internal fault there can send a false high voltage to the park brake control module.
Extremely rare; a PCM internal short could backfeed voltage into the park brake control circuit, but this is the least likely cause.
It means the voltage on the signal wire that the park brake control module monitors is above the expected maximum, often near battery voltage when it should be low or switching.
Yes, the vehicle is usually drivable, but the electric parking brake may not function correctly. You should ensure the mechanical parking brake (if equipped) works and have the issue diagnosed promptly to avoid being unable to secure the vehicle.
No. While a faulty module is possible, the most common cause is a wiring short to voltage. Replacing the module without checking the circuit often does not fix the problem.
It is extremely unlikely. The PCM is rarely involved in the park brake control circuit. Replacing the PCM for this code is almost never the correct repair and should only be considered after exhaustive testing rules out all other causes.