P1574

DTC P1574

DTC Descriptor

DTC P1574 00
- Stop Lamp Switch Circuit

Diagnostic Fault Information

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

Circuit/System Description

The stop lamp switch signal circuit is a direct hardwire input to the throttle actuator control (TAC) module from the body control module (BCM). The TAC module monitors the stop lamp switch signal circuit in order to detect when the brake pedal has been applied. When the brake pedal is pressed, the BCM sends a class 2 serial data message to the powertrain control module (PCM) indicating that the brake pedal has been applied. The BCM also sends a high voltage signal on the stop lamp switch signal circuit to the TAC module. The TAC module sends a universal asynchronous receiver transmitter (UART) serial data message to the PCM indicating that a brake pedal application has occurred. The PCM will compare the UART serial data message and the class 2 serial data message in order to confirm that both serial data messages match.

Conditions for Running the DTC

* DTC P0573 is 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.

Conditions for Setting the DTC

* The PCM detects that there is a 4.2 km/h (2.6 mph) or greater decrease in vehicle speed within 0.25 seconds.
* The TAC module does not detect a voltage signal on the stop lamp switch signal circuit.

Action Taken When the DTC Sets

* The cruise control system is disabled.
* The PCM stores the DTC information into memory when the diagnostic runs and fails.
* The malfunction indicator lamp (MIL) will not illuminate.
* The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.

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 PCM receives the clear code command from the scan tool.

Diagnostic Aids

* Inspect for proper operation of the stop lamps.
* For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections in Diagnostic Aids. Component Tests and General Diagnostics

Circuit/System Verification

1. Ignition ON, verify that DTC P0504 is not current in the PCM.

• If the specified DTC is current, refer to Diagnostic Trouble Code (DTC) List - Vehicle. Diagnostic Trouble Code Descriptions

2. Verify that the stop lamps operate properly.

• If the stop lamps do not operate properly, refer to Stop Lamps Inoperative. Stop Lamps Inoperative

Circuit/System Testing

1. Ignition ON, verify that the Stop Lamp Pedal Switch parameter reads Released.

• If the parameter reads Applied, refer to Stop Lamps Always On. If the stop lamps operate normal, replace the PCM. Stop Lamps Always On

2. Verify that the Stop Lamp Pedal Switch parameter reads Released when depressing the brake pedal.

• If the parameter reads Applied, test the stop lamp switch signal circuit between TAC module terminal 6 and S141 for an open/high resistance. If the circuit tests normal, replace the TAC module.

3. Ignition OFF, disconnect the harness connector at the PCM. Verify that a test lamp illuminates between stop lamp switch signal terminal 32 and ground when the brake pedal is depressed.

• If the test lamp does not illuminate, test the signal circuit for an open/high resistance.

4. If all circuits test normal, replace the PCM.

Repair Instructions

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

Programming and Relearning for PCM or TAC \e89774752>