P1574

DTC P1574

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* 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 00
- Stop Lamp 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.

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

* The history DTC clears after 40 malfunction-free warm-up cycles.
* The DTC becomes history when the conditions for setting the DTC are no longer present.
* The ECM receives the clear code command from the scan tool.

Diagnostic Aids

Ensure the stop lamps operate properly. Refer to Exterior Lighting Systems Description and Operation in order to avoid misdiagnosis.

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. 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 stop lamp switch.

2. Disconnect the stop lamp switch.
3. Ignition ON, test for B+ at terminal D of the stop lamp switch harness.

^ If less than the specified value, test the ignition voltage supply circuit for an open/high resistance or short to ground.

4. Reconnect the stop lamp 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 stop lamp switch.

5. If all circuit and component tests are normal, replace the ECM.

Component Testing

1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
2. Test for less than 1 ohm resistance between terminals C and D of the switch.

^ If not the specified value, replace the stop lamp switch.

3. Depress the brake pedal. Test for infinite resistance between terminals C and D of the switch.

^ If not the specified value, replace the stop lamp switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Stop Lamp Switch Replacement