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 cruise release brake switch without a transition of the stop lamp switch, the PCM 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 seconds. |
| • | The PCM detects a cruise release brake 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. |
| • | The PCM receives a clear code command from the scan tool. |
Diagnostic Aids
| • | Inspect for proper adjustment of the cruise release switch. Refer to Cruise Release Switch Adjustment . |
| • | Refer to Exterior Lighting Systems Description and Operation in Lighting Systems In order to avoid a misdiagnosis. |
| • | For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference : Cruise Control Schematics Connector End View Reference: Cruise Control Connector End Views | |||
1 | Did you perform the Cruise Control Diagnostic System Check? | Go to Step 2 | |
2 | Do the stop lamps operate properly? | Go to Step 3 | Go to Stop Lamps Inoperative or Stop Lamps Always On in Lighting Systems |
3 | Test the stop lamp switch signal circuit for an open or the high resistance. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. 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 PCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 6 | Go to Step 5 |
5 |
Important: Program the replacement powertrain control module (PCM). Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 2.8L (LK5) or to Powertrain Control Module Replacement in Engine Controls - 3.5L (L52). Did you complete the replacement? | Go to Step 6 | -- |
6 |
Does the DTC reset? | Go to Step 2 | System OK |
