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
- Stop Lamp Switch Circuit
Diagnostic Fault Information
Circuit/System Description
The stop lamp switch signal circuit is a direct hardwire input from the body control module (BCM) to the powertrain control module (PCM) and the throttle actuator control (TAC) module. The modules monitor the stop lamp switch signal circuit to detect when the brake pedal has been applied. When the brake pedal is applied, the BCM sends a serial data message to the modules and also a voltage signal on the stop lamp switch signal circuit indicating that the brake pedal has been applied.
Conditions for Running the DTC
* The engine speed is greater than 700 RPM.
* The traction control system or the antilock brake system are not active.
* The vehicle speed is greater than 48 km/h (30 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 TAC module does not detect a voltage signal on the stop lamp switch signal circuit.
* The PCM does not detect a stop lamp switch transition.
Actions Taken When the DTC Sets
* The cruise control system is disabled.
* The malfunction indicator lamp (MIL) will not illuminate.
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)
* Engine Controls 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 Testing
1. Ignition OFF, disconnect the harness connectors at the appropriate control modules listed below.
* ECM X2 module and TCM (LY7)
* ECM X1 module and TCM (LS4)
* PCM X1 module and TAC (L26)
2. Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
* TAC terminal 6 (L26)
* TCM terminal 42 (LS4/LY7)
3. Ignition ON, verify the test lamp illuminates ON and OFF while pressing and releasing the brake pedal.
• If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.
• If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
4. Ignition OFF, connect the harness connector at the TCM or TAC.
5. Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
* ECM terminal 59 (LY7)
* ECM terminal 29 (LS4)
* PCM terminal 32 (L26)
6. Ignition ON, verify the test lamp illuminates ON and OFF while pressing and releasing the brake pedal.
• If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the appropriate TCM or TAC.
7. If all circuits tests normal, replace the appropriate ECM with (LS4/LY7), or PCM with (L26).
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
Control Module References (Programming and Relearning) for BCM, ECM, PCM, TCM or TAC module replacement, setup, and programming