Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC P1574: Stop Lamp Switch CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
B+ | P1574 | P1574 | -- | -- |
Stop Lamp Switch Signal | P0571 | P0571 | P0571 | -- |
Stop Lamp Switch Control | P0571 | P0571 | -- | -- |
TCC Brake Switch/Cruise Control Release Signal | P1574 | P1574 | P1574 | -- |
Circuit/System Description
The brake switch/cruise control release switch and the stop lamp switch are incorporated into an assembly and are mounted to the brake pedal bracket. When the brake pedal is pressed, the normally closed brake switch/cruise control release switch opens and the normally open stoplamp switch closes. This creates a low signal voltage on the brake switch/cruise control release switch signal circuit and 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 engine control module (ECM) detects that there is a 4.2 km/h (2.6 mph) or greater decrease in vehicle speed within 0.25 second and a transition of the torque converter clutch (TCC) brake switch circuit without a transition of the stop lamp switch circuit, the ECM sets DTC P1574.
Conditions for Running the DTC
| • | DTCs P0502, P0503, P0719, and P0724 are not set. |
| • | 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 vehicle speed decreases by at least 4.2 km/h (2.6 mph) within 0.25 second. |
| • | The ECM detects a TCC brake transition. |
| • | The ECM does not detect a stop lamp switch transition. |
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 in order to avoid misdiagnosis.
Reference Information
Schematic Reference
Connector End View Reference
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 TCC/Cruise Brake Pedal parameter while applying and releasing the brake pedal. The reading should change between Applied/Released, and all brake lights should turn ON and OFF accordingly.
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.
- Ignition OFF, reconnect the stop lamp switch. Ignition ON, verify the Stoplamp Pedal Switch parameter displays Released.
- Apply the brake pedal. Verify the Stoplamp Pedal Switch parameter displays Applied.
- If all circuit tests normal, replace the ECM or PCM.
| • | B+ circuit terminals C and E (with JE3/C4 or JE4) |
| • | B+ circuit terminals B and D (with JE3/C5/C6/C7) |
| ⇒ | If less than the specified value, test the B+ circuit for a short to ground or an open/high resistance. |
| ⇒ | If the parameter displays Applied, test the signal circuit terminal D (with JE3/C4 or JE4) or terminal C (with JE3/C5/C6/C7) for a short to voltage. If the circuit tests normal, test or replace the stop lamp switch. |
| ⇒ | If the parameter displays Released, test the signal circuit terminal D (with JE3/C4 or JE4) or terminal C (with JE3/C5/C6/C7) for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the stoplamp switch. |
Component Testing
- Ignition OFF, disconnect the harness connector at the stop lamp switch.
- Test for less than 1 ohm between the switch terminals C and D.
- Depress the brake pedal. Test for infinite resistance between the switch terminals C and D.
| ⇒ | If not the specified value, replace 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.
| • | Control Module References for ECM or PCM module replacement, setup, and programming |
