P1574
DTC P1574
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC P1574
- Stoplamp Switch Circuit
Diagnostic Fault Information
Circuit/System Description
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) in order to enable the diagnostic.
* 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 ECM sets the stop lamp switch status to released.
* 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
* Cruise Control Schematics (Electrical Diagrams)
* Exterior Lights Schematics (Exterior Lights Schematics)
* Antilock Brake System Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Cruise Control Description and Operation (Description and Operation)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
Ignition ON, observe the TCC/Cruise Brake 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 accordingly.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal B and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the signal circuit terminal A for a short to ground.
3. Verify the scan tool TCC/Cruise Brake Pedal Switch parameter displays Released.
• If not the specified value, test the signal circuit terminal A for a short to voltage. If the circuit tests normal, replace the ECM.
4. Install a 3A fused jumper wire between the signal circuit terminal A and the B+ circuit terminal B. Verify the scan tool TCC/Cruise Brake Pedal Switch parameter displays Applied.
• If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
5. If all circuits test normal, test or replace the stop lamp switch.
Component Testing
1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
2. Test for infinite resistance between the signal circuit terminal A and B+ terminal B with the switch in the open position.
• If not the specified value, replace the stop lamp switch.
3. Test for less than 1 ohm between the signal terminal A and B+ terminal B with the switch in the closed position.
• If greater than the specified range, replace the stop lamp switch.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Stop Lamp Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for ECM, PCM module replacement, setup, and programming