Circuit Description
The body control module (BCM) receives a signal from the brake pedal position sensor through the stop lamp switch signal circuit. The BCM then applies voltage through the stop lamp voltage supply circuit to the powertrain control module (PCM), engine control module (ECM) and the stop lamps.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0504 Brake Switch 1-2 Correlation
Conditions for Running the DTC
| • | The vehicle has cycled from 0-60 km/h (0-37 mph) 3 times in 1 ignition cycle. |
| • | Continuous once the previous criteria have been met. |
Conditions for Setting the DTC
| • | Both discrete input and serial data message brake applied/unapplied data do not match for at least 2 seconds, for 10 occurrences. |
| • | Invalid voltage signal on the stop lamp signal for at least 2 seconds. |
Action Taken When the DTC Sets
| • | The ECM stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records. |
Conditions for Clearing the DTC
| • | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Use a scan tool in order to clear the DTC. |
Diagnostic Aids
| • | Verify that the brake pedal position sensor is adjusted properly. Refer to Brake Pedal Position Sensor Calibration . |
| • | Test drive the vehicle if a switch or circuit condition cannot be located. An intermittent condition may be duplicated during a test drive. |
| • | For an intermittent, refer to Testing for Intermittent Conditions and Poor Connections . |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Exterior Lights Schematics Connector End View Reference: Master Electrical Component List | |||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||||
Does the stop lamp signal parameter indicate ON? | Go to Step 3 | Go to Diagnostic Aids | |||||||
3 | Test for the following in the stop lamp voltage supply circuit to the ECM:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 5 | Go to Step 4 | ||||||
4 | Replace the body control module (BCM). Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 5 | -- | ||||||
5 |
Does the DTC reset? | Go to Step 2 | System OK | ||||||
