P0573

SYMPTOM
P0573-BRAKE SWITCH 1 STUCK OFF

WHEN MONITORED
Ignition on.

SET CONDITION
When the PCM recognizes Brake Switch No.1 is stuck in the high/off position. One Trip Fault. Three good trips to turn off the MIL.

POSSIBLE CAUSES
- (B29) BRAKE SWITCH NO.1 SIGNAL 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





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. STOP LAMP SWITCH





Turn the ignition off.
Disconnect the Stop Lamp Switch harness connector.
Measure the resistance between the (Z429) Ground circuit terminal and the (B29) Brake Switch No.1 Signal 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?
Yes>> Go To 3
No>> Replace the Stop Lamp Switch. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-4.

3. (B29) BRAKE SWITCH NO.1 SIGNAL CIRCUIT OPEN





Turn the ignition off. Disconnect the PCM harness connectors.

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 (B29) Brake Switch No.1 Signal 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 (B29) Brake Switch No.1 Signal 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 the (Z429) Ground circuit and ground 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. 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.