3T40 Automatic Transmission

Diagnostic Chart:

Schematic:

Circuit Description with 3T40 Automatic Transmission
The brake switch indicates brake pedal status to the Powertrain Control Module (PCM). The normally-closed switch supplies battery voltage on circuit 420 to the PCM. Applying the brake pedal opens the brake switch, interrupting voltage to the PCM. While the brake pedal is not applied, the PCM receives constant voltage. If the PCM receives 0 volts at the brake switch input with the Torque Converter Clutch (TCC) engaged, the PCM de-energizes the torque converter clutch solenoid valve (TCC solenoid valve). When the PCM detects a closed brake switch circuit (12 volts, high input) during decelerations, then DTC P0724 sets. DTC P0724 is a type C DTC.

CONDITIONS FOR RUNNING THE DTC
The ignition is in the ON position.

CONDITIONS FOR SETTING THE DTC
DTC P0724 sets if the PCM detects a closed brake switch or circuit (12 volts) during vehicle deceleration and the following conditions occur eight consecutive times:
^ The vehicle speed is greater than 32 km/h (20 mph) for 6 seconds
^ then the vehicle speed is 8-32 km/h (5-20 mph) for 3 seconds
^ then the vehicle speed remains less than 8 km/h (5 mph).

ACTION TAKEN WHEN THE DTC SETS
^ The PCM does not illuminate the Malfunction Indicator Lamp (MIL).
^ The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Failure Records.
^ The PCM stores DTC P0724 in PCM history.

CONDITIONS FOR CLEARING THE DTC
^ A scan tool can clear the DTC.
^ The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission related diagnostic fault occurring.

DIAGNOSTIC AIDS
^ Inspect the brake switch for proper adjustment.
^ Inspect the connectors at the PCM, the brake switch and all other circuit connecting points for an intermittent condition. Refer to Testing for Intermittent and Poor Connections in Diagrams.
^ Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical Intermittents in Diagrams.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. If you disconnect the brake switch connector and observe the Scan Tool brake switch status change, then a brake switch problem is the only possible cause of the DTC.
3. An unchanging brake switch status (Closed) in step 2 indicates a possible short to power in the input circuit.
4. If the brake switch is properly adjusted, then you must replace the brake switch.
5. Replace the PCM only after you have completed the preceding diagnostic steps.