For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | 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: Stoplamp Switch Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
B+ | P1574 | P1574 | -- |
Cruise Control Release Switch Signal | P1574 | P1574 | P1574 | --

### 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.

### Actions Taken When the DTC Sets

• | The malfunction indicator lamp (MIL) will not illuminate.

• | 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.

### Diagnostic Aids

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

### Reference Information

#### Schematic Reference

Cruise Control Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Cruise Control Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References 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 and Released.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the cruise control release switch.
2. Ignition ON, test for B+ between the B+ circuit terminal 1 and ground.

⇒ | If less than the specified value, test the B+ circuit for a short to ground or an open/high resistance.

3. Verify the scan tool TCC/Cruise Brake Pedal Switch parameter displays Released.

⇒ | If not the specified value, test the signal circuit terminal 2 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 2 and the B+ circuit terminal 1. Verify the scan tool TCC/Cruise Brake Pedal Switch parameter displays Applied.

⇒ | If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

5. If all circuits test normal, test or replace the cruise control release switch.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the cruise control release switch.
2. Test for less than 1 ohm between terminals 1 and 2 at the switch.

⇒ | If not the specified value, replace the cruise control release switch.

3. Depress the brake pedal. Test for infinite resistance between terminals 1 and 2 at the switch.

⇒ | If not the specified value, replace the cruise control release switch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Cruise Control Release Switch Replacement

• | Control Module References for ECM module replacement, setup, and programming