Transmission Diagnosis

Diagnostic Chart:

Schematic:

Circuit Description with 4L80-E / 4L85-E Automatic Transmission
The normally open TCC/Stoplamp switch indicates brake pedal status to the Powertrain Control Module (PCM). Applying the brake pedal closes the switch, supplying voltage to the PCM. Releasing the brake pedal interrupts voltage to the PCM.

If the PCM detects a closed TCC/Stoplamp switch (stuck ON) during accelerations, then DTC P0724 sets. DTC P0724 is a type C DTC.

CONDITIONS FOR RUNNING THE DTC
^ No OSS DTCs P0722 or P0723.
^ The following sequence of events occur:
- The vehicle speed is less than 8 km/h (5 mph).
- The vehicle speed is 8-32 km/h (5-20 mph) for greater than 3.1 seconds.
- The vehicle speed is greater than 32 km/h (20 mph) for 7 seconds.

CONDITIONS FOR SETTING THE DTC
^ All the conditions for running the DTC are met for eight occurrences.
^ The PCM detects a closed TCC/Stoplamp switch circuit (12 volts).
^ The brake switch is ON for greater than 900 seconds (15 minutes).

ACTION TAKEN WHEN THE DTC SETS
^ The PCM does not illuminate the Malfunction Indicator Lamp (MIL).
^ For TCC scheduling, the PCM disregards the TCC/Stoplamp switch state if the APP sensor is greater than 0.5% and the vehicle speed is greater than 40 Km/h (25 mph).
^ 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 nor-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.
^ First diagnose and clear any engine DTCs 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.
2. This step isolates the TCC/Stoplamp switch as a source for setting the DTC.