Diagnostic Instructions
DTC Descriptors
DTC P0571: Cruise Control Brake Switch Circuit
DTC P0572: Brake Switch Circuit 1 Low Voltage
DTC P0573: Brake Switch Circuit 1 High Voltage
Diagnostic Fault Information
Circuit
| Short to Ground
| Open or High Resistance
| Short to Voltage
| Signal Performance
|
Stop Lamp Switch Signal
| P0571 or P0572
| P0571 or P0572
| P0571 or P0573
| P0571, P0572 or P0573
|
Circuit/System Description
The stop lamp switch signal circuit is a high voltage input from the body control module (BCM) to the engine control module (ECM) and the transmission control module (TCM). The ECM monitors the stop lamp switch circuit to detect when the brake pedal has
been applied. The BCM monitors the brake pedal position sensor to determine when the brake pedal is applied. When the brake pedal is applied, the BCM supplies a high voltage signal on the stop lamp switch signal circuit and also sends a serial data message to
the ECM indicating that the brake pedal has been applied. The ECM senses a high voltage signal on the stop lamp switch signal circuit when the brake pedal has been applied.
Conditions for Running the DTC
• | Battery voltage is greater than 11.5 volts. |
Conditions for Setting the DTC
The ECM detects either a low voltage signal on the stop lamp switch signal circuit when the serial data message from the BCM indicates the brakes are applied, or 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 after 40 malfunction-free ignition cycles have occurred. |
Reference Information
Schematic Reference
Cruise Control Schematics
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 appropriate control modules listed below.
- Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
• | TCM terminal F38 (5L40E) |
- 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 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 ECM module.
- Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
• | TCM terminal F38 (5L40E) |
- Ignition ON, 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 a short to ground or an open/high resistance. If the circuit test normal, replace the ECM. |
- If all circuits test normal, replace the TCM.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for BCM, ECM, or TCM replacement, setup, and programming