Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC P0572 : Brake Switch Circuit 1 Low VoltageDTC P0573: Brake Switch Circuit 1 High Voltage
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Stop Lamp Switch Signal | P0572 P1574 | P0572 P1574 | P0573 | -- |
Circuit/System Description
The stop lamp switch signal circuit is a direct hardwire input from the body control module (BCM) to the engine control module (ECM) with (LS4), or the powertrain control module (PCM) with (L26), transmission control module (TCM) and throttle actuator control (TAC) module (as equipped). The modules monitor the stop lamp switch signal circuit to detect when the brake pedal has been applied. The BCM monitors the brake apply sensor signal circuit to determine when the brake pedal is applied. When the brake pedal is applied, the BCM sends a serial data message to the modules and also a voltage signal on the stop lamp switch signal circuit indicating that the brake pedal has been applied.
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/PCM 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/PCM 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
Connector End View Reference
Description and Operation
Cruise Control Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the harness connectors at the appropriate control modules listed below.
- Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
- Ignition ON, verify the test lamp illuminates ON and OFF while pressing and releasing the brake pedal.
- Ignition OFF, connect the harness connector at the TCM.
- Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
- Ignition ON, verify the test lamp illuminates ON and OFF while pressing and releasing the brake pedal.
- If all circuits tests normal, replace the appropriate ECM with (LS4), or PCM with (L26).
| • | ECM X1 and TCM (LS4) |
| • | PCM X1 and TAC (L26) |
| • | TAC terminal 6 (L26) |
| • | TCM terminal 42 |
| ⇒ | If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM. |
| ⇒ | 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 BCM. |
| • | PCM terminal 32 (L26) |
| • | ECM terminal 7 (LS4) |
| ⇒ | 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 appropriate TCM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for BCM, ECM, PCM, TAC or TCM module replacement, setup, and programming
