P0571

P0571-BRAKE SWITCH 1 PERFORMANCE

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The brake switch rationality checks both failure modes of the brake switch. The brake switch stuck on test checks for a high vehicle speed condition where the brake switch is unexpectedly depressed. The brake switch stuck off test checks for repeated vehicle stop maneuvers without the brake switch depressed.

- When Monitored:
With the ignition on.

- Set Condition:
If the output of Brake Switch No.1 signal to the Powertrain Control Module (PCM) does not match the Brake Switch Output circuit to the BCM for 0.5 seconds. Two Trip Fault.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

Diagnostic Test

1. ACTIVE DTC

NOTE: Make sure the Stop Lamp Switch is properly adjusted before continuing.

1. Ignition on, engine not running.
2. With the scan tool, select View DTCs.
3. Press and release the Brake Pedal.

Is the DTC Active at this time?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.

2. CHECK THE (B135) BRAKE SWITCH NO.1 SIGNAL CIRCUIT FOR A SHORT TO GROUND
1. Turn the ignition off.
2. Disconnect the Stop Lamp Switch harness connector.
3. Disconnect the PCM C1 harness connector.
4. Measure the resistance between ground and the (B135) Brake Switch No.1 Signal circuit at the Stop Lamp Switch harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 3

No

- Repair the short to ground in the (B135) Brake Switch No.1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

3. CHECK THE (B135) BRAKE SWITCH NO.1 SIGNAL CIRCUIT FOR AN OPEN
1. Disconnect the PCM C1 harness connector.
2. Measure the resistance of the (B135) Brake Switch No.1 Signal circuit between the Stop Lamp Switch harness connector and the appropriate terminal of the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 4

No

- Repair the open in the (B135) Brake Switch No.1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

4. STOP LAMP SWITCH
1. Measure the resistance between terminal 1 and terminal 2 at the Stop Lamp Switch.
2. Next, measure the resistance between terminal 3 and terminal 4 at the Stop Lamp Switch.
3. Apply and release the Stop Lamp Switch while monitoring the Ohmmeter.

Does the resistance change from below 5.0 Ohms to an open circuit for one or both of the measurements taken?

Yes

- Go To 5

No

- Verify that there is good pin to terminal contact in the Switch and Powertrain Control Module harness connectors. If OK, replace the Stop Lamp Switch. Stop Lamp Switch - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

5. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Stop Lamp Switch and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Switch and Powertrain Control Module harness connectors.
4. Perform any Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Powertrain Control Module. .
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.