Circuit 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 class 2 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 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 multifunction 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 .
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Cruise Control Schematics Connector End View Reference: Engine Control Module Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 | Do the stop lamps operate properly? | Go to Step 3 | Go to Stop Lamps Inoperative or to Stop Lamps Always On |
3 |
Does the Stoplamp 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 body control module (BCM) and the engine control module (ECM). Refer to Circuit Testing and to Wiring Repairs . 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 BCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . 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 . Did you find and correct the condition? | Go to Step 9 | Go to Step 8 |
7 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 9 | -- |
8 | Replace the ECM. Refer to Control Module References 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 |
