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. |
| • | Use a scan tool in order to clear the DTC. |
Diagnostic Aids
In order to avoid a misdiagnosis, inspect for proper operation of the stop lamps. Refer to
Exterior Lighting Systems Description and Operation
.
For an intermittent condition, refer to
Testing for Intermittent Conditions and Poor Connections
.
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Scan Tool Data List
Circuit/System Testing
- Ignition ON, verify that the Stop Lamp Pedal Switch parameter in the ECM reads Released while depressing the brake pedal.
| ⇒ | If the Stop Lamp Pedal Switch parameter reads Applied, replace the ECM. |
- Ignition OFF, 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.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
Control Module References
for BCM or ECM replacement, setup, and programming
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 from the engine control module (ECM) to the transmission control module (TCM) and 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 ECM sends a high voltage signal on the stop lamp switch signal circuit to the BCM. 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 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. |
| • | Use a scan tool in order to clear the DTC. |
Diagnostic Aids
Important: Repair any brake system related DTCs before performing this diagnostic.
| • | This DTC may be stored as a history DTC without affecting the operation of the ECM. If stored only as a history DTC and not retrieved as a current DTC, do not replace the BCM or ECM. |
| • | If this DTC is retrieved as both a current and a history DTC, replace the ECM. |
Reference Information
Schematic Reference
Exterior Lights Schematics
Connector End View Reference
Lighting Systems Connector End Views
Electrical Information Reference
Scan Tool Reference
Scan Tool Data List
Circuit/System Testing
Important: Fix any Brake System related DTCs or symptoms before using this diagnostic.
- Ignition ON, perform the brake pedal position (BPP) sensor calibration procedure and verify the BPP is calibrated properly. Refer to
Brake Pedal Position Sensor Calibration
.
| ⇒ | If the BPP will not calibrate properly, replace the BPP. |
- Ignition ON, observe the BPP Circuit Signal parameter in the ECM while depressing the brake pedal.
| ⇒ | If the parameter reads Applied, 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 ECM. |
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
