Diagnostic Instructions
DTC Descriptor
DTC P0571: Stop lamp Switch Circuit
Diagnostic Fault Information
Circuit
| Short to Ground
| Open/High Resistance
| Short to Voltage
| Signal Performance
|
Stop Lamp Switch B+
| P0571
| P0571
| --
| --
|
Stop Lamp Switch Signal
| P0571
| P0571
| P0571
| --
|
Circuit/System Description
The stop lamp switch is mounted to the brake pedal bracket. When the brake pedal is pressed, the normally open stoplamp switch closes. This creates a high signal voltage on the stop lamp switch signal circuit.
This diagnostic test functions on the assumption that a sudden decrease in vehicle speed is caused by a brake pedal application. When the ECM detects that there is a 4.2 km/h (2.6 mph) or greater decrease in vehicle speed within 0.25 seconds without a
transition of the stop lamp switch, the ECM sets DTC P0571.
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). |
| • | The diagnostic will disable when the wheel speed is less than 16 km/h (10 mph). |
Conditions for Setting the DTC
| • | The ECM detects that there is a 4.2 km/h (2.6 mph) or greater decrease in vehicle speed within 0.25 seconds without a transition of the stop lamp switch. |
| • | The above condition is present for greater than 1.5 seconds. |
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. |
Diagnostic Aids
Verify the stop lamps operate properly. Refer to
Exterior Lighting Systems Description and Operation.
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 Verification
Ignition ON, observe the Stoplamp Pedal Switch parameter while applying and releasing the brake pedal. The reading should change between Applied/Released, and all brake lights should turn ON and OFF.
Circuit/System Testing
- Ignition OFF, disconnect the stop lamp switch.
- Ignition ON, test for B+ between the appropriate B+ circuit terminal listed below and ground.
| • | B+ circuit terminals terminal B (with JE3) |
| • | B+ circuit terminal D (with JE4) |
| ⇒ | If less than the specified value, test the B+ circuit for a short to ground or an open/high resistance. |
- Ignition OFF, reconnect the stop lamp switch. Ignition ON, verify the Stoplamp Pedal Switch parameter displays Released.
| ⇒ | If the parameter displays Applied, test the signal circuit terminal C (with JE4) or terminal A (with JE3) for a short to voltage. If the circuit tests normal, test or replace the stop lamp switch. |
- Apply the brake pedal. Verify the Stoplamp Pedal Switch parameter displays Applied.
| ⇒ | If the parameter reads Released, test the signal circuit terminal A (with JE3) or terminal C (with JE4) for an open/high resistance or short to ground. If the circuit tests normal, test or replace the stop lamp switch. |
- If all circuits test normal, replace the ECM.
Component Testing
- Ignition OFF, disconnect the harness connector at the stop lamp switch.
- Test for infinite resistance between the appropriate switch terminals listed below.
| • | terminals A and B (with JE3) |
| • | terminals C and D (with JE4) |
| ⇒ | If not the specified value, replace the stop lamp switch. |
- Depress the brake pedal. Test for less than 1 ohm between the appropriate switch terminals listed below.
| • | terminals A and B (with JE3) |
| • | terminals C and D (with JE4) |
| ⇒ | If not the specified value, replace the stop lamp switch. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
