Circuit Description
The engine control module (ECM) monitors the stop lamp switch signal circuit and the cruise control release signal circuit every 100 ms. The ECM monitors the status of the stop lamp switch signal circuit and the cruise control signal circuit to see if they match when the brake pedal is pressed or released.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
The status of the stop lamp switch input to the ECM, and the cruise/brake switch input to the ECM do not match for at least 2 seconds continuously, for 10 occurrences. Each time the signals match then do not match at counter increments. When the counter reaches 10 the DTC will set.
Action Taken When the DTC Sets
When DTC P0504 is set the following will occur:
| • | The cruise control is disabled. |
| • | The ECM will function as if the brake pedal is not pressed. |
| • | The control module stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records. |
Conditions for Clearing the DTC
| • | The DTC will clear when the status of the stop lamp switch input to the ECM, and the cruise/brake switch input to the ECM match for at least 2 seconds continuously for both the pressed position and the released position. |
| • | A current DTC Last Test Failed clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Diagnostic Aids
| • | Inspect for proper adjustment of the stop lamp switch and cruise/brake switch. Refer to Cruise Release Switch Adjustment in Cruise Control and Stop Lamp Switch Adjustment . |
| • | Check for internments and poor connections. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Exterior Lights Schematics and Cruise Control Schematics in Cruise Control Connector End View Reference: Master Electrical Component List in Wiring Systems | |||
1 | Did you perform the Diagnostic System Check - Lighting Systems? | Go to Step 2 | |
2 |
Does the Brake Switch parameter and the Cruise Brake Switch parameter display change closely with each other? | Go to Diagnostic Aids | Go to Step 3 |
3 |
Does the Cruise Brake Switch parameter display change with the brake pedal position? | Go to Step 6 | Go to Step 4 |
4 |
Does the Cruise Brake Switch parameter display Applied? | Go to Step 5 | Go to Step 12 |
5 |
Does the Cruise Brake Switch parameter display Released? | Go to Step 16 | Go to Step 8 |
6 |
Does the Brake Switch parameter display Released? | Go to Step 7 | Go to Step 10 |
7 |
Does the Brake Switch parameter display Applied? | Go to Step 15 | Go to Step 11 |
8 | Test the ignition positive voltage circuit of the cruise/brake switch for an open, high resistance, or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 20 | Go to Step 9 |
9 | Test for an open, high resistance, or short to ground in the cruise control release signal circuit of the cruise/brake switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 20 | Go to Step 14 |
10 | Test the stop lamp switch signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 20 | Go to Step 14 |
11 | Test the battery positive voltage circuit of the stop lamp switch for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 20 | Go to Step 13 |
12 | Test the cruise control release signal circuit of the cruise/brake switch for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 20 | Go to Step 17 |
13 | Test the stop lamp switch signal circuit for an open, high resistance, or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 20 | Go to Step 14 |
14 | Inspect for poor connections at the harness connector of the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 20 | Go to Step 17 |
15 | Inspect for poor connections at the harness connector of the cruise/brake switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 20 | Go to Step 18 |
16 | Inspect for poor connections at the harness connector of the stop lamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 20 | Go to Step 19 |
17 |
Important: Program the replacement ECM. Replace the ECM. Refer to Engine Control Module Replacement in Engine Controls - 3.0L (L81). Did you complete the replacement? | Go to Step 20 | -- |
18 | Replace the stop lamp switch. Refer to Stop Lamp Switch Replacement . Did you complete the replacement? | Go to Step 20 | -- |
19 | Replace the cruise/brake switch. Refer to Cruise Control Release Switch Replacement in Cruise Control. Did you complete the replacement? | Go to Step 20 | -- |
20 |
Does the DTC reset? | Go to Step 2 | System OK |
