Home » GM 6.5 » GM/Detroit 6.5L – Engine Management – BRAKE SWITCHES AND CLUTCH PEDAL POSITION SWITCH – Description

GM/Detroit 6.5L – Engine Management – BRAKE SWITCHES AND CLUTCH PEDAL POSITION SWITCH – Description

The PCM uses brake switch input information to interrupt cruise control operation when the brakes are applied. On automatic transmission vehicles, there are two brake switches: a normally open cruise control brake switch and a normally closed torque converter clutch (TCC) brake switch. Both send signals to the PCM alerting it to disengage cruise control.
Both are housed in the stoplamp switch assembly located at the brake pedal. Manual transmission vehicles feature a normally closed clutch pedal position switch in place of the TCC brake switch.

Circuit Operation
The cruise control brake switch receives battery power on CKT 140 (figure 5-54). When the brakes are applied, the switch closes, allowing a battery positive signal to travel to the PCM on CKT 820. The PCM reads this circuit to know the brakes are engaged. This information is also used to illuminate the vehicle stoplamps.

The TCC brake switch receives power from the ignition switch on CKT 439. When the brakes are applied, the TCC brake switch opens, disengaging TCC. The PCM recognizes TCC brake switch status by the absence of a voltage signal on CKT 420.

The clutch pedal position switch on manual transmissions performs the same function as the TCC brake switch. In its normally closed position, it transmits a voltage signal to the PCM on CKT 86. When the brakes are applied, the switch opens, interrupting the flow of voltage to the PCM.

DTC 41 — “Brake Switch Circuit Fault”
DTC 41 is the result of the brake inputs not toggling on moderate braking. It sets when the vehicle is decelerating and the TCC (or clutch pedal position) and cruise control brake switches are not toggling “open” and “closed” during 6 brake applications in the same ignition cycle.

 

Leave a Reply

Your email address will not be published. Required fields are marked *