P0572
DTC P0572 or P0573
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC P0572
-
Brake Switch Circuit 1 Low Voltage
DTC P0573
-
Brake Switch Circuit 1 High Voltage
Diagnostic Fault Information
Circuit/System Description
The stop lamp switch signal circuit is an ignition voltage input to the body control module (BCM), electronic brake control module, engine control module (ECM), transmission control module (TCM), Power Take Off (PTO) module (if equipped) and Trailer Brake controller (if equipped). The BCM monitors the stop lamp switch circuit to detect when the brake pedal has been applied. The ECM monitors the stop lamp switch signal to determine when the brake pedal is applied. When the brake pedal is applied, the BCM sends a serial data message to the ECM indicating that the brake pedal has been applied. The ECM senses an ignition voltage signal on the brake switch signal circuit when the stop lamp switch is closed.
Conditions for Running the DTC
* The engine is running.
* Battery voltage is greater than 11.5 V.
Conditions for Setting the DTC
P0572
The ECM detects a low voltage signal on the stop lamp switch signal circuit for more than 2 seconds when the serial data message from the BCM indicates the brakes are applied. The ECM sets the DTC when the condition has been detected 8 out of 10 times.
P0573
The ECM detects a high voltage signal on the stop lamp switch signal circuit for more than 2 seconds when the serial data message from the BCM indicates the brakes are released. The ECM sets the DTC when the condition has been detected 8 out of 10 times.
Actions Taken When the DTC Sets
* The malfunction indicator lamp (MIL) will not illuminate.
* The cruise control system is disabled.
Conditions for Clearing the DTC
* The condition responsible for setting the DTC no longer exists.
* A history DTC will clear after 40 malfunction-free ignition cycles have occurred.
Diagnostic Aids
Ensure all the stop lamps operate properly. Refer to Exterior Lighting Systems Description and Operation Exterior Lighting Systems to avoid misdiagnosis. If the vehicle stop lamps operate improperly, refer to Symptoms - Lighting Symptoms - Lighting.
Reference Information
Schematic Reference
* Cruise Control Schematics Electrical Diagrams
* Exterior Lights Schematics Exterior Lights Schematics
Connector End View Reference
Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
Description and Operation
Cruise Control Description and Operation Description and Operation
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
2. Ignition ON, verify a test lamp illuminates between the ignition circuit terminal B and ground.
• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
3. Ignition OFF, disconnect the X1 harness connector at the ECM.
4. Ignition ON, test for less than 1 V between the signal circuit terminal listed below and ground.
* Gas 4.3L - terminal 55
* Gas, except 4.3L - terminal 9
* Diesel - terminal 83
* HP2 - terminal 7
Note:
Because the signal circuit is used by multiple modules, it may be necessary to disconnect each module, one at a time, while monitoring the voltage on the circuit. If the voltage is eliminated when a particular module is disconnected, the short to voltage is occurring on the branch of the circuit or at that module. Also, the signal circuit provides voltage to the trailer provision. A short to voltage or voltage backfeed in the customers trailer wiring may cause this DTC to set, often in an intermittent manner.
• If greater than the specified range, test the signal circuit for a short to voltage.
5. Ignition OFF, connect the X1 harness connector at the ECM.
6. Ignition ON, verify the scan tool ECM BPP Circuit Signal parameter is Released.
• If not the specified value, replace the ECM.
7. Connect a 3 A fused jumper between the B+ circuit terminal B and the signal circuit terminal A. Verify the scan tool ECM BPP Circuit Signal parameter is Applied.
• If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
8. If all circuits test normal, test or replace the stop lamp switch.
Component Testing
1. Ignition OFF, disconnect the stop lamp switch.
2. With the brake pedal released, test for infinite resistance between terminal A and terminal B stop lamp switch.
• If not the specified value, replace the stop lamp switch.
3. With the brake pedal released, test for less than 1.0 ohms between terminal C and terminal D at the stop lamp switch.
• If not the specified value, replace the stop lamp switch.
4. With the brake pedal applied, test for less than 1.0 ohms between terminal A and terminal B at the stop lamp switch.
• If not the specified value, replace the stop lamp switch.
5. With the brake pedal applied, test for infinite resistance between terminal C and terminal D at the stop lamp switch.
• If not the specified value, replace the stop lamp switch.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Control Module References Control Module References for ECM replacement, programming and setup