P1574
DTC P1574
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) 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 without a transition of the stop lamp switch, 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.
Action Taken When the DTC Sets
* The ECM sets the stop lamp switch status to released.
* The ECM disables the operation of the cruise control system.
Conditions for Clearing the DTC
* A current DTC will clear when 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
Ensure the stop lamps operate properly. Refer to Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation) in order to avoid misdiagnosis.
Reference Information
Schematic Reference
Cruise Control Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
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 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. Verify the cruise control release switch is properly adjusted. Refer to Cruise Release Switch Adjustment (Adjustments) .
2. Ignition ON, verify the TCC/Cruise Brake Pedal parameter displays Released.
• If the parameter reads Applied, test the TCC Brake Switch/Cruise Control Release Signal circuit for a short to voltage. If the circuit tests normal, test or replace the cruise control release switch.
3. Disconnect the cruise control release switch.
4. Test for B+ at terminal 1 of the cruise control release switch.
• If less than the specified value, test the circuit for an open/high resistance or short to ground.
5. Reconnect the cruise control release switch and apply the brake pedal. Verify the TCC/Cruise Brake Pedal parameter displays Applied.
• If the parameter reads Released, test the TCC Brake Switch/Cruise Control Release Signal circuit for an open/high resistance or short to ground. If the circuit tests normal, test or replace the cruise control release switch.
6. If all circuits and components test normal, replace the ECM.
Component Testing
1. Verify the cruise control release switch is properly adjusted. Refer to Cruise Release Switch Adjustment (Adjustments) .
2. Ignition OFF, disconnect the harness connector at the cruise control release switch.
3. Test for less than 1 ohm resistance between terminals 1 and 2 of the switch.
• If not the specified value, replace the cruise control release switch.
4. Depress the brake pedal. Test for infinite resistance between terminals 1 and 2 of the switch.
• If not the specified value, replace the cruise control release switch.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Cruise Control Release Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for ECM module replacement, setup, and programming