P0571

P0571-BRAKE SWITCH 1 PERFORMANCE





For a complete wiring diagram Consult Diagrams/Electrical.

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:
Ignition on.

- Set Condition:
If the output of Brake Switch No.1 to the PCM looks like it is not applied, while Brake Lamp Switch Output circuit is applied the fault will mature in 60ms. One Trip Fault.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview.

Diagnostic Test

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

NOTE: Make sure the Stop Lamp Switch is properly wired, such as (B84) Brake Signal 1 and (B86) Brake Signal 2 circuit are not switched at the harness connector.

Ignition on, engine not running.
With a scan tool, select View DTCs.
Is the DTC Active at this time?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Checking for an Intermittent DTC.

2. (B84) BRAKE SIGNAL 1 SHORTED TO GROUND




Turn the ignition off.
Disconnect the Stop Lamp Switch harness connector.
Disconnect the C4 PCM harness connector.
Measure the resistance between ground and the (B84) Brake Signal 1 circuit in the Stop Lamp Switch harness connector.
Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the (B84) Brake Signal 1 circuit.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Go To 3

3. (B84) BRAKE SIGNAL 1 CIRCUIT OPEN




Measure the resistance of the (B84) Brake Signal 1 circuit from the Stop Lamp Switch harness connector to the C4 PCM harness connector.
Is the resistance below 5.0 ohms?

Yes

- Go To 4

No

- Repair the open in the (B84) Brake Signal 1 circuit.
- Perform the PCM Verification Test. PCM Verification Test.

4. (B86) BRAKE SIGNAL 2 CIRCUIT OPEN




Measure the resistance of the (B86) Brake Signal 2 circuit from the Stop Lamp Switch harness connector to the C4 PCM harness connector.
Is the resistance below 5.0 ohms?

Yes

- Go To 5

No

- Repair the open in the (B86) Brake Signal 2 circuit.
- Perform the PCM Verification Test. PCM Verification Test.

5. (B86) BRAKE SIGNAL 2 CIRCUIT SHORTED TO GROUND




Measure the resistance between ground and the (B86) Brake Signal 2 circuit in the Stop Lamp Switch harness connector.
Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the (B86) Brake Signal 2 circuit.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Go To 6

6. (Z905) GROUND CIRCUIT OPEN




Measure the resistance between ground and the (Z905) Ground circuit in the Stop Lamp Switch harness connector.
Is the resistance below 5.0 ohms?

Yes

- Go To 7

No

- Repair the open in the (Z905) Ground circuit.
- Perform the PCM Verification Test. PCM Verification Test.

7. STOP LAMP SWITCH
Measure the resistance between the (Z905) Ground circuit terminal and the (B84) Brake Signal 1 terminal in the Stop Lamp Switch.
Next, measure the resistance between the (F202) Fused Ignition Switch circuit terminal and the (B86) Brake Signal 2 circuit terminal in the Stop Lamp Switch.
Apply and release the brake pedal 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 8

No

- Replace the Stop Lamp Switch.
- Perform the PCM Verification Test. PCM Verification Test.

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

Yes

- Repair as necessary.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Replace and program the Powertrain Control Module.
- Perform the PCM Verification Test. PCM Verification Test.