P0573
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 brake pedal position (BPP) sensor is used to sense the action of the driver application of the brake pedal. The BPP sensor provides an analog voltage signal that will increase as the brake pedal is applied. The instrument panel module (IPM) provides a low reference signal and a 5-volt reference voltage to the BPP sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the IPM will apply battery voltage to the center high mounted stop lamp (CHMSL), transmission control module (TCM), engine control module (ECM), and stop lamp relay. When the stop lamp relay receives battery voltage from the IPM, the relay coil is energized and the stop lamp relay switch contacts close applying battery voltage through the stop lamps fuse to illuminate the stop lamps. Ground for the left stop lamp and CHMSL is provided at G402 and the right stop lamp is grounded at G401.
Conditions for Running the DTC
* The engine is running.
* Battery voltage is greater than 11.5 volts.
Conditions for Setting the DTC
P0572
The ECM detects a low voltage signal on the stop lamp switch signal circuit when the serial data message from the BCM indicates the brakes are applied.
P0573
The ECM detects a high voltage signal on the stop lamp switch signal circuit when the serial data message from the BCM indicates the brakes are not applied.
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 once 40 malfunction-free ignition cycles have occurred.
Reference Information
Schematic Reference
Exterior Lights Schematics (Exterior Lights Schematics)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Exterior Lighting Systems Description and Operation (Exterior Lighting Systems)
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 (Programming and Relearning) for scan tool information
Circuit/System Verification
With a scan tool, command the stop lamps ON and OFF. The stop lamps should turn ON and OFF when changing between the commanded states.
If the stop lamps do not illuminate when commanded, refer to Stop Lamps Malfunction (Stop Lamps Malfunction).
Circuit/System Testing
1. Ignition OFF, disconnect the harness connectors at the appropriate control modules listed below.
* ECM X1 - with LH2/LC3
* ECM X2 - with LLT
* TCM
2. Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
* ECM terminal 7 - with LH2/LC3
* ECM terminal 52 - with LLT
* TCM terminal 8
3. Ignition ON, verify the test lamp turns ON and OFF when pressing and releasing the brake pedal.
• If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the stop lamp relay.
• If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the stop lamp relay.
4. Ignition OFF, connect the harness connector at the TCM.
5. Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
* ECM terminal 7 - with LH2/LC3
* ECM terminal 52 - with LLT
6. Ignition ON, verify the test lamp turns ON and OFF when pressing and releasing the brake pedal.
• If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the TCM.
• If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the TCM.
7. If all circuits test normal, replace the ECM.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Control Module References (Programming and Relearning) for ECM to TCM replacement, setup, and programming