P0571

SYMPTOM
P0571 BRAKE SWITCH 1 PERFORMANCE

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 Out put circuit is applied the fault will mature in 60 ms. One Trip Fault.

POSSIBLE CAUSES
- (B29) BRAKE SWITCH NO.1 SIGNAL SHORTED TO GROUND
- (L50) BRAKE LAMP SWITCH OUTPUT CIRCUIT OPEN
- (L50) BRAKE LAMP SWITCH OUTPUT CIRCUIT SHORTED TO GROUND
- (Z429) GROUND CIRCUIT OPEN
- STOP LAMP SWITCH
- PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Scan Tool Testing and Procedures

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 (B29) Brake Switch No.1 and (L50) Brake Lamp Switch Output circuit are not switched at the harness connector.

Ignition on, engine not running.
With a scan tool, read DTCs.
Is the DTC active at this time?
Yes>> Go To 2
No>> Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4. Powertrain Verification Test - Ver 4

2. (B29) BRAKE SWITCH NO.1 SIGNAL SHORTED TO GROUND





Turn the ignition off.
Disconnect the Stop Lamp Switch harness connector.
Disconnect the PCM harness connectors.
Measure the resistance between ground and the (B29) Brake Switch No.1 Signal circuit in the Stop Lamp Switch harness connector.
Is the resistance below 100 ohms?
Yes>> Repair the short to ground in the (B29) Brake Switch No.1 Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
No>> Go To 3

3. (L50) BRAKE LAMP SWITCH OUTPUT CIRCUIT OPEN





Disconnect the C1 FCM harness connector.
Measure the resistance of the (L50) Brake Lamp Switch Output circuit from the Stop Lamp Switch harness connector to the C1 FCM harness connector.
Is the resistance below 5.0 ohms?
Yes>> Go To 4
No>> Repair the open in the (L50) Brake Lamp Switch Output circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.

4. (L50) BRAKE LAMP SWITCH OUTPUT CIRCUIT SHORTED TO GROUND





Measure the resistance between ground and the (L50) Brake Lamp Switch Output circuit in the Stop Lamp Switch harness connector.
Is the resistance below 100 ohms?
Yes>> Repair the short to ground in the (L50) Brake Lamp Switch Output circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.
No>> Go To 5

5. (Z429) GROUND CIRCUIT OPEN





Measure the resistance between ground and the (Z429) 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 (Z429) Ground circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.

6. STOP LAMP SWITCH








Measure the resistance between the (Z429) Ground circuit terminal and the (B29) Brake Switch No.1 Signal terminal in the Stop Lamp Switch.
Next, measure the resistance between the (A103) Fused B+ circuit terminal and the (L50) Brake Lamp Switch Output 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 (NGC) POWERTRAIN VERIFICATION TEST VER-4.

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 (NGC) POWERTRAIN VERIFICATION TEST VER-4.
No>> Replace and program the Powertrain Control Module per Service Information. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.