For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptor

DTC P0719: Brake Switch Circuit Low Voltage
DTC P0724: Brake Switch Circuit High Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Signal | P0719 | P0719 | P0724 | --

### Circuit/System Description

The brake switch indicates brake pedal status to the transmission control module (TCM). The normally-open brake switch supplies ignition voltage to the TCM. Applying the brake pedal closes the switch, resumes voltage to the TCM. Releasing the brake pedal interrupts voltage to the TCM.

### Conditions for Running the DTC

#### P0719

• | No output speed sensor (OSS) DTCs P0722 or P0723.

• | Brake Switch DTC P0724 has not passed.

• | The TCM detects the brake switch is apply for 900 seconds.

• | The vehicle speed is less than 8 km/h (5 mph) for greater than 6 seconds, then greater than 40 km/h (25 mph) for 6 seconds.

• | Continuously 8 times once the previous criteria have been met.

• | This DTC has not passed this ignition cycle.

#### P0724

• | No OSS DTCs P0722 or P0723.

• | No Brake Switch DTC P0719.

• | The vehicle speed is less than 40 km/h (25 mph) for 6 seconds, then greater than 40 km/h (25 mph) for 7 seconds, then less than 8 km/h (5 mph).

### Conditions for Setting the DTC

#### P0719

The TCM detects an open or short to ground on the stop lamp switch signal circuit during 8 consecutive vehicle accelerations.

#### P0724

The TCM detects the brake switch circuit is open during accelerations.

### Action Taken When the DTC Sets

DTC P0719 and P0724 are Type C DTCs.

### Conditions for Clearing the DTC

DTC P0719 and P0724 are Type C DTCs.

### 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.

• | It may be necessary to also clear this DTC from the engine control module (ECM).

### Reference Information

#### Schematic Reference

Automatic Transmission Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Transmission General Information

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Transmission Control Module Scan Tool Information

#### Special Tools

J 35616 GM-Approved Terminal Test Kit

### Circuit/System Verification

1. Ignition ON, observe the scan tool Brake Switch parameter while applying and releasing the brake pedal. The reading should change between Applied and Released.
2. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal B and ground.

⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test the signal circuit terminal A for a short to ground.

3. Verify the scan tool Brake Switch is Released.

⇒ | If not the specified value, test the signal circuit terminal A for a short to voltage. If the circuit tests normal, replace the TCM.

4. Install a 3A fused jumper wire between the signal circuit terminal A and the ignition, circuit terminal B. Verify the scan tool Brake Switch is applied.

⇒ | If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the TCM.

5. If all circuits test normal, test or replace the stop lamp switch.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
2. Test for infinite resistance between the signal terminal A and the ignition terminal B with the switch in the open position.

⇒ | If not the specified value, replace the stop lamp switch.

3. Test for less than 10 ohms of resistance between the signal terminal A and the ignition terminal B with the switch in the closed position.

⇒ | If greater than the specified range, replace the brake switch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• | Stop Lamp Switch Replacement

• | Control Module References for TCM replacement, setup, and programming.