Diagnostic Instructions
DTC Descriptor
DTC P0571: Cruise Control Brake Switch Circuit
Diagnostic Fault Information
Circuit
| Short to Ground
| Open/High Resistance
| Short to Voltage
| Signal Performance
|
Stop Lamp Switch Signal
| P0571
| P0571
| --
| P0571
|
Circuit/System Description
The brake switch signal circuit is a high voltage input to the body control module (BCM), engine control module (ECM), transmission control module (TCM), Power Take Off (PTO) module (if equipped) and Trailer Brake controller (if equipped). The BCM monitors
the stop lamp switch circuit to detect when the brake pedal has been applied. The ECM monitors the brake switch signal to determine when the brake pedal is applied. When the brake pedal is applied, the BCM sends a serial data message to the ECM indicating that
the brake pedal has been applied. The ECM senses a high voltage signal on the brake switch signal circuit when the stop lamp switch is closed.
Conditions for Running the DTC
| • | Battery voltage is greater than 11.5 volts. |
Conditions for Setting the DTC
The ECM detects a low voltage signal on the brake switch signal circuit when the serial data message from the BCM indicates the brakes are applied.
Actions Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The cruise control system is disabled. |
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists. |
| • | A history DTC will clear after 40 malfunction-free ignition cycles have occurred. |
Reference Information
Schematic Reference
Connector End View Reference
Component Connector End Views
Description and Operation
Cruise Control Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the stop lamp switch.
- Ignition ON, test for B+ between the B+ circuit terminal B and ground.
| ⇒ | If less than the specified value, test the B+ circuit for a short to ground or an open/high resistance. |
- Verify the BPP Circuit Signal data parameter displays released.
| ⇒ | If not the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
- Connect a 3A fused jumper between the B+ circuit terminal B and the signal circuit terminal A. Verify the BPP Circuit Signal data parameter displays applied.
| ⇒ | If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM. |
- If all circuits test normal, test or replace the stop lamp switch.
Component Testing
- Ignition OFF, disconnect the stop lamp switch.
- With the brake pedal released, test for infinite resistance between terminal A and terminal B stop lamp switch.
| ⇒ | If not the specified value, replace the stop lamp switch. |
- With the brake pedal released, test for less than 1.0 ohm between terminal C and terminal D at the stop lamp switch.
| ⇒ | If not the specified value, replace the stop lamp switch. |
- With the brake pedal applied, test for less than 1.0 ohm between terminal A and terminal B at the stop lamp switch.
| ⇒ | If not the specified value, replace the stop lamp switch. |
- With the brake pedal applied, test for infinite resistance between terminal C and terminal D at the stop lamp switch.
| ⇒ | If not the specified value, replace the stop lamp switch. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
