For 1990-2009 cars

### Circuit Description

This diagnostic test functions on the assumption that a sudden decrease in vehicle speed is caused by a brake pedal application. When the powertrain control module (PCM) detects that there is a 4.2 km/h (2.6 mph) or greater decrease in vehicle speed within 0.25 seconds and a transition of the torque converter clutch (TCC) brake/cruise release switch without a transition of the stop lamp switch, the PCM sets DTC P1574.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1574 Stop Lamp Switch Circuit

### 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 (TCS) or the Antilock Brake System (ABS) 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 seconds.

• | The PCM detects a TCC brake/cruise release switch transition.

• | The PCM does not detect a stop lamp switch transition.

### Action Taken When the DTC Sets

• | The PCM sets the stop lamp switch status to released.

• | The PCM disables the operation of the Cruise Control System.

### Conditions for Clearing the DTC

• | A history DTC will clear after 40 malfunction free warm-up cycles, if failures are not reported by this or any other emission related diagnostic.

• | The PCM receives a clear code command from the scan tool.

### Diagnostic Aids

• | Inspect for proper adjustment of the TCC brake/cruise release switch. Refer to Cruise Release Switch Adjustment .

• | Refer to Exterior Lighting Systems Description and Operation in order to avoid a misdiagnosis.

• | For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections .

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference : Cruise Control Schematics Connector End View Reference: Cruise Control Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Do the stop lamps operate properly? | Go to Step 3 | Go to Stop Lamps Inoperative or Stop Lamps Always On
3 | Test the stop lamp switch signal circuit for an open or the high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and complete the repair? | Go to Step 6 | Go to Step 4
4 | Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 6 | Go to Step 5
5 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 6 | --
6 |

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC.

Does the DTC reset?

Go to Step 2

System OK