Diagnostic Instructions
DTC Descriptors
DTC P0572 : Brake Switch Circuit 1 Low Voltage
DTC 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
| P0572
| 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), and the transmission control module (TCM). 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
| • | 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
| • | Stop lamp switch input is ignored. Brake apply status is obtained through serial data messages. |
| • | The cruise control system becomes 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. |
Reference Information
Schematic Reference
Connector End View Reference
Component Connector End Views
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 modules listed below.
- Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
| • | TCM terminal 42 (ME7 or MN5) |
- Ignition ON, press and release the brake pedal. 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 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. |
- Ignition OFF, connect the harness connector at the TCM.
- Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
| • | ECM terminal 9 X1 (LZ4) |
| • | ECM terminal 7 X1 (LAT or LYZ) |
- Ignition ON, press and release the brake pedal. Verify the test lamp turns ON and OFF when pressing and releasing the brake pedal.
| ⇒ | If the test lamp is always OFF, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM. |
| ⇒ | 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 all circuits test normal, replace the ECM.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for BCM, ECM or TCM replacement, setup, and programming
