Diagnostic Instructions
DTC Descriptor
DTC P0571: Stop Lamp Switch Circuit
Circuit/System Description
The stop lamp switch signal circuit is a direct hardwire input to the throttle actuator control (TAC) module from the body control module (BCM). The TAC module 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 powertrain control module (PCM) 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 TAC module. The TAC module sends a universal asynchronous receiver transmitter (UART) serial data message to the PCM indicating that a brake pedal application has occurred. The PCM will compare the UART serial data message and the class 2 serial
data message in order to confirm that both serial data messages 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. |
| • | The vehicle speed is greater than 48 km/h (30 mph) in order to enable the diagnostic. |
Conditions for Setting the DTC
| • | The PCM detects that there is a 4.2 km/h (2.6 mph) or greater decrease in vehicle speed within 0.25 second. |
| • | The TAC module does not detect a voltage signal on the stop lamp switch signal circuit. |
Action Taken When the DTC Sets
| • | The cruise control system is disabled. |
| • | The PCM stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records. |
Conditions for Clearing the DTC
| • | The history DTC clears after 40 malfunction-free warm-up cycles. |
| • | The DTC becomes history when the conditions for setting the DTC are no longer present. |
| • | The PCM receives the clear code command from the scan tool. |
Diagnostic Aids
Reference Information
Schematic Reference
Cruise Control Schematics
Connector End View Reference
Electrical Information Reference
Electrical Information Reference
Scan Tool Reference
Scan Tool Data List
Circuit/System Verification
- Ignition ON, verify that DTC P1574 is not current in the PCM.
- Verify that the stop lamps operate properly.
Circuit/System Testing
- Ignition ON, verify that the Stop Lamp Pedal Switch parameter reads Released.
| ⇒ | If the parameter reads Applied, refer to
Stop Lamps Always On. If the stop lamps operate normal, replace the PCM. |
- Verify that the Stop Lamp Pedal Switch parameter reads Released when depressing the brake pedal.
| ⇒ | If the parameter reads Applied, test the stop lamp switch signal circuit between TAC module terminal 6 and S141 for an open/high resistance. If the circuit tests normal, replace the TAC module. |
- Ignition OFF, disconnect the harness connector at the PCM. Verify that a test lamp illuminates between stop lamp switch signal terminal 32 and ground when the brake pedal is depressed.
| ⇒ | If the test lamp does not illuminate, test the signal circuit for an open/high resistance. |
- If all circuits test normal, replace the PCM.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for PCM or TAC module replacement, setup, and programming
