DTC P0571: Cruise/Brake Switch Circuit: Description

Ignition voltage is supplied to ECM through cruise brake switch (switch closed with brake pedal released) whenever ignition is turned on. Once brake pedal is applied, cruise brake switch opens circuit and ECM cruise brake switch input goes low. ECM stoplight switch input operates opposite. ECM stoplight switch input is 5-7 volts (due to an ECM internal resistor configuration) with brake pedal released (switch open). Input will go high (ignition voltage) with brake applied (switch closed). ECM monitors both switch inputs against each other to verify that a circuit has not failed. DTC sets when ECM detects conflicting cruise brake switch and stoplight switch inputs for a certain length of time and a certain number of times.