Circuit Description
The brake switch indicates brake pedal status to the powertrain control module (PCM). The brake switch is a normally-closed switch that supplies battery voltage on circuit 420 to the PCM. Applying the brake pedal opens the switch, interrupting voltage to the PCM. When the brake pedal is released, the PCM receives a constant voltage signal. If the PCM receives a zero voltage signal at the brake switch input, and the torque converter clutch (TCC) is engaged, the PCM de-energizes the TCC solenoid valve. The PCM disregards the brake switch input for TCC scheduling if there is a brake switch circuit fault (Refer to Diagnostic Aids).
When the PCM detects an open brake switch circuit (0 volts, low input) during accelerations, then DTC P0719 sets. DTC P0719 is a type D DTC.
Conditions for Running the DTC
| • | No VSS assembly DTCs P0502 or P0503. |
| • | The ignition switch is in the ON position. |
Conditions for Setting the DTC
The PCM detects an open brake switch circuit (0 volts) for 15 minutes without changing for 2 seconds, and the following events occur seven times:
| • | The vehicle speed is less than 8 km/h (5 mph); |
| • | then the vehicle speed is 8-32 km/h (5-20 mph) for 4 seconds; |
| • | then the vehicle speed is greater than 32 km/h (20 mph) for 6 seconds. |
Action Taken When the DTC Sets
| • | The PCM does not illuminate the malfunction indicator lamp (MIL). |
| • | The PCM disregards the brake switch input for TCC scheduling. |
| • | The PCM stores DTC P0719 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 brake 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 condition, massage the wiring harness while watching the test equipment for a change. |
| • | If the PCM detects a brake switch circuit fault, then the brake switch input is disregarded for TCC scheduling. The PCM then uses throttle position and vehicle speed to determine TCC application and release. Use of these inputs may result in a noticeable harsh apply or abrupt release of the TCC. |
| • | Ask about the customer's driving habits. Ask about unusual driving conditions (e.g. stop and go, expressway, etc.). |
| • | Inspect the brake switch for proper mounting and operation. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
2 |
Important: Before clearing the DTC, use the scan tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the PCM. Is the test lamp ON? | -- | ||
Install a fused jumper wire from terminal A to terminal B of the brake switch connector. Did the TCC Brake Switch status change from Open to Closed? | -- | |||
4 |
Refer to General Electrical Diagnosis in Wiring Systems. Is the fuse open? | -- | ||
5 |
Important: The condition that affects this circuit may exist in other connecting branches of the circuit. Refer to Electrical Diagnosis for complete circuit distribution. Refer to General Electrical Diagnosis in Wiring Systems. Refer to Wiring Repairs in Wiring Systems. Was a short to ground condition found? | -- | ||
6 |
Refer to General Electrical Diagnosis in Wiring Systems. Refer to Wiring Repairs in Wiring Systems. Was a short to ground condition found? | -- | ||
7 | Replace the brake switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes. Is the replacement complete? | -- | -- | |
8 |
Important: The condition that affects this circuit may exist in other connecting branches of the circuit. Refer to Electrical Diagnosis for complete circuit distribution. Refer to General Electrical Diagnosis in Wiring Systems. Refer to Wiring Repairs in Wiring Systems. Was an open condition found? | -- | -- | |
9 |
Refer to General Electrical Diagnosis in Wiring Systems. Refer to Wiring Repairs in Wiring Systems. Was an open condition found? | -- | ||
10 | Replace the PCM. Refer to Powertrain Control Module/Throttle Actuator Control Module Replacement in Engine Controls. Is the replacement complete? | -- | -- | |
11 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | System OK |
