Normal Operation

The stoplamp switch is a single plunger 2 stage switch with 2 inputs to the PCM. When the brake pedal is applied, the first stage, which is a normally open stoplamp switch, closes and sends a voltage signal to the PCM deactivating the cruise control, if engaged. The second stage is the normally closed cruise control deactivator switch (integral to the stoplamp switch) opens and removes the ground signal to the PCM when the brake pedal is firmly applied. This is a redundant signal to the PCM. There is less than one millimeter in plunger travel between the first and second stage which the PCM monitors.

• DTC P0504 (Brake Switch A / B Correlation) - sets when the PCM does not sense the correct sequence of the brake pedal input signal from both the cruise control deactivator and stoplamp switches when the brake pedal is pressed and released.
• DTC P0572 (Brake Switch A Circuit Low) - sets when the PCM detects an open in the stoplamp switch signal. The PCM monitors the vehicle speed, the engine speed, the engine torque and the stoplamp BOO input during start and stop driving cycles. If the BOO input to the PCM is always off during start and stop driving cycles this DTC sets in continuous memory.
• DTC P0573 (Brake Switch A Circuit High) - sets when the PCM detects an short to voltage on the stoplamp switch signal. The PCM monitors the vehicle speed, the engine speed, the engine torque and the stoplamp BOO input during start and stop driving cycles. If the BOO input to the PCM is always on during start and stop driving cycles this DTC sets in continuous memory.

This pinpoint test is intended to diagnose the following: 

• Wiring, terminals or connectors
• Cruise control deactivator switch (integral to the stoplamp switch)
• Stoplamp switch
• PCM