4L80-E / 4L85-E Automatic Transmission

Circuit Description
The TCC/Stoplamp switch indicates the brake pedal status. The normally closed brake switch supplies a B+ signal on CKT 420 to the powertrain control module
(PCM). The signal voltage circuit opens when the brakes are applied.
If the PCM detects a closed TCC/Stoplamp switch during decelerations, then DTC P0724 sets. DTC P0724 is a type D DTC.

Conditions for Running the DTC
^ No OSS DTC P0502.
^ The following sequence of events occurs 10 consecutive times:
1. The vehicle speed is greater than 40 km/h (25 mph) for 6 seconds.
2. Then the vehicle speed is 8-40 km/h (5-25 mph) for 4 seconds.
3. Then the vehicle speed is less than 8 km/h (5 mph).

Conditions for Setting the DTC
^ All conditions are met for 10 occurrences.
^ The PCM detects a closed TCC/Stoplamp switch circuit (12 volts) during decelerations.

Action Taken When the DTC Sets
^ The PCM does not illuminate the malfunction indicator lamp (MIL).
^ The PCM stores DTC P0724 in PCM history.

Conditions for Clearing the DTC
^ A scan tool clears the DTC from PCM history.
^ The PCM clears the DTC from PCM history if the vehicle completes 40 consecutive warm-up cycles without a non-emission-related diagnostic fault occurring.
^ The PCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the PCM.

Diagnostic Aids
^ Inspect the wiring at the PCM, the TCC/Stoplamp switch connector and all other circuit connecting points for the following conditions:
- A backed out terminal
- A damaged terminal
- Reduced terminal tension
- A chafed wire
- A broken wire inside the insulation
- Moisture intrusion
- Corrosion
^ When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
^ Ask about the customer's driving habits and any unusual driving conditions he or she might have, such as stop and go traffic or expressway driving.
^ Inspect the brake switch for proper mounting and adjustment.
^ Inspect for the most current calibration ID and the latest bulletins.
^ First diagnose and clear any engine DTCs or TP sensor codes that are present. Then inspect for any transmission DTCs that may have reset.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
3. This step isolates the TCC/Stoplamp switch as a source f6r setting the DTC.