Diagnostic Instructions
DTC Descriptor
DTC P0571 00: Cruise Control Brake Switch Circuit
Circuit/System Description
The stop lamp switch signal circuit is a direct hardwire input to the engine control module (ECM) from the body control module (BCM). The ECM monitors the stop lamp switch signal circuit in order to detect when the brake pedal has been applied. When the
brake pedal is pressed, the BCM sends a serial data message to the ECM indicating that the brake pedal has been applied. The BCM also sends a high voltage signal on the stop lamp switch signal circuit to the ECM. This DTC will set if the serial data message
and the voltage signal on the stop lamp switch signal circuit do not match.
Conditions for Running the DTC
| • | The engine speed is greater than 700 RPM. |
| • | The traction control system or the antilock brake system are not active and have not failed. |
Conditions for Setting the DTC
| • | The ECM detects that there is a 8.3 km/h (5.1 mph) or greater decrease in vehicle speed within 1 second. |
| • | The ECM detects that the class 2 serial data message and the voltage signal on the stop lamp switch signal circuit do not match for 10 consecutive times that this diagnostic is run. |
| • | The above condition is present for greater than 2 seconds. |
Action Taken When the DTC Sets
| • | The cruise control system is disabled. |
| • | The ECM stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records. |
Conditions for Clearing the DTC
| • | A last test failed, or the current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if failures are not reported by this or any other emission related diagnostic. |
Reference Information
Schematic Reference
Cruise Control Schematics
Connector End View Reference
Cruise Control Connector End Views
Description and Operation
Cruise Control Description and Operation
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
In order to avoid a misdiagnosis, inspect for proper operation of the stop lamps. Refer to
Exterior Lighting Systems Description and Operation
in Lighting Systems.
Circuit/System Testing
- Ignition ON, verify that the Stop Lamp Pedal Switch parameter in the ECM reads Applied while depressing the brake pedal.
| ⇒ | If the Stop Lamp Pedal Switch parameter reads Released, test the stop lamp switch signal circuit for an open/high resistance, a short to ground, or a short to voltage. If the circuit tests normal, replace the BCM. |
- 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 or ECM replacement, setup, and programming.
