4L80-E / 4L85-E Automatic Transmission
DTC P0724 (6.6L)
Circuit Description
The stop lamp switch indicates the brake pedal status to the transmission control module (TCM). The brake switch is a normally-closed switch that supplies battery voltage on the CHMSL supply voltage circuit to the TCM. Applying the brake opens the stop lamp switch, interrupting voltage to the TCM. When the brake is released, the TCM receives a constant voltage signal input. If the TCM receives a 0 voltage signal input at the CHMSL supply voltage circuit, and the torque converter clutch (TCC) is engaged, the TCM de-energizes the TCC solenoid valve. The TCM disregards the brake switch input for TCC scheduling if there is a brake switch circuit fault.
When the TCM detects an open brake switch circuit during accelerations, then DTC P0724 sets. DTC P0724 is a type C DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0724 Brake Switch Circuit High Voltage
Conditions for Running the DTC
* No OSS DTCs P0722 or P0723.
* The vehicle speed is less than 8 km/h (5 mph), then the vehicle speed is between 8 km/h (5 mph) and 40 km/h (25 mph) for 6 seconds or less, then the vehicle speed is greater than 40 km/h (25 mph) for greater than 5 seconds.
Conditions for Setting the DTC
The TCM detects the brake switch circuit is open 8 times during acceleration cycles and the brake switch voltage is high for 900 seconds (15 minutes) or greater.
Action Taken When the DTC Sets
* The TCM does not request the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL).
* The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM records this information as a Failure Record.
* The TCM stores DTC P0724 in TCM history.
Conditions for Clearing the DTC
* A scan tool can clear the DTC.
* The TCM clears the DTC from TCM 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 mounting and operation.
* Inspect for ABS DTCs. A faulty ABS condition may contribute to setting DTC P0724.
Test Description
The number below refers to the step number on the diagnostic table.
2. This step isolates the brake switch as a source for setting the DTC.
Step 1 - Step 6:
