Code P0577 indicates the powertrain control module (PCM) has detected a voltage signal from the cruise control input circuit that is higher than the expected range. This usually points to a fault in the brake switch, cruise control switch, or related wiring.
The brake switch is the most common cause. A stuck or misadjusted switch can send a constant high signal to the PCM, preventing cruise control operation.
A wire in the cruise control circuit may be pinched, chafed, or shorted to battery voltage, causing a high input signal.
The cruise control on/off, set, or resume switch can fail internally, sending an incorrect high voltage signal.
Poor connections at the brake switch, cruise control module, or PCM can create intermittent high resistance or voltage spikes.
In very rare cases, the PCM itself may have an internal fault causing a false high reading. This should only be considered after all other components and wiring have been thoroughly tested.
Yes, a burned-out or incorrect brake light bulb can sometimes cause a voltage drop or feedback that triggers this code. Always check brake light operation first.
Almost never. The PCM is rarely the cause of P0577. Most cases are fixed by replacing the brake switch, repairing wiring, or replacing the cruise control switch. Only consider PCM replacement after all other possibilities have been exhausted and confirmed by a professional.
Yes, the vehicle is generally safe to drive, but cruise control will not function. If the brake lights are affected, driving may be unsafe. Have the issue diagnosed promptly.
Clearing the code may turn off the Check Engine Light temporarily, but if the underlying fault remains, the code will return. The root cause must be repaired.