P0571

P0571-BRAKE SWITCH 1 PERFORMANCE





For a complete wiring diagram refer to 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:

With the gear selector in drive, vehicle speed above a minimum value, and battery voltage greater than 10.4 volts.

- 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.


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 (B15) Brake Signal 1 and (B16) 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. Intermittent Condition


2. (B15) BRAKE SIGNAL 1 SHORTED TO GROUND





Turn the ignition off.

Disconnect the Stop Lamp Switch harness connector.

Disconnect the C3 PCM harness connector.

Measure the resistance between ground and the (B15) 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 (B15) Brake Signal 1 circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 3


3. (B16) BRAKE SIGNAL 2 CIRCUIT OPEN





CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.

Measure the resistance of the (B16) Brake Signal 2 circuit from the Stop Lamp Switch harness connector to the appropriate terminal of special tool #8815.

Is the resistance below 5.0 ohms?

Yes

- Go To 4

No

- Repair the open in the (B16) Brake Signal 2 circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test


4. (B16) BRAKE SIGNAL 2 CIRCUIT SHORTED TO GROUND





Measure the resistance between ground and the (B16) 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 (B16) Brake Signal 2 circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 5


5. (Z910) GROUND CIRCUIT OPEN





Measure the resistance between ground and the (Z910) Ground circuit in the Stop Lamp Switch harness connector.

Is the resistance below 5.0 ohms?

Yes

- Go To 6

No

- Repair the open in the (Z910) Ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test


6. STOP LAMP SWITCH

Measure the resistance between the (Z910) Ground circuit terminal and the (B15) Brake Signal 1 terminal in the Stop Lamp Switch.

Next, measure the resistance between the (F943) Fused Ignition Switch circuit terminal and the (B16) 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 7

No

- Replace the Stop Lamp Switch.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test


7. PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

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