Circuit Description
The stop lamp switch signal circuit is a direct hardwire input to the engine control module (ECM) from the electronic brake control module (EBCM). 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 EBCM sends a class 2 serial data message to the ECM indicating that the brake pedal has been applied. The EBCM also sends a high voltage signal on the stop lamp switch signal circuit to the ECM. This DTC will set if the class 2 serial data message and the voltage signal on the stop lamp switch signal circuit do not match.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0571 Cruise Control Brake Switch Circuit
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 in Lighting Systems.
For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Cruise Control Schematics Connector End View Reference: Engine Control Module Connector End Views in Engine Controls - 3.6L (LY7) | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 | Do the stop lamps operate properly? | Go to Step 3 | Go to Stop Lamps Inoperative or to Stop Lamps Always On in Lighting Systems |
3 |
Does the Stop Lamp Pedal Switch parameter display Applied? | Go to Step 5 | Go to Step 4 |
4 | Test the stop lamp switch signal circuit for an open or for a high resistance between the electronic brake control module (EBCM) and the ECM. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 6 |
5 | Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 7 |
6 | Inspect for poor connections at the harness connector of the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 8 |
7 | Replace the EBCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 9 | -- |
8 | Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 9 | -- |
9 |
Does the DTC reset? | Go to Step 2 | System OK |
