Circuit Description
The engine control module (ECM) monitors the stop lamp switch signal circuit and the torque converter clutch (TCC) brake switch/cruise control release signal circuit every 100 ms. The ECM monitors the status of the stop lamp switch signal circuit and the TCC brake switch/cruise control signal circuit to see if they match when the brake pedal is pressed or released.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0504 Brake Switch Circuit 1-2 Correlation
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 TCC brake switch/cruise control 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 a 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 TCC brake switch/cruise control 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
| • | Aftermarket trailer brake controllers must be disconnected before diagnosing DTC P0504 due to they could result in incorrect diagnostics. |
| • | Check for intermittents and poor connections. Refer to Testing for Intermittent Conditions and Poor Connections . |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Exterior Lights Schematics and Cruise Control Schematics Connector End View Reference: Master Electrical Component List | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Does the Stop Lamp Pedal Switch parameter and TCC/Cruise Brake Pedal Switch parameter display change closely with each other? | Go to Diagnostic Aids | Go to Step 3 |
3 |
Does the TCC/Cruise Brake Pedal Switch parameter display change with the brake pedal position? | Go to Step 6 | Go to Step 4 |
4 |
Does the TCC/Cruise Brake Pedal Switch parameter display released? | Go to Step 5 | Go to Step 12 |
5 |
Does the TCC/Cruise Brake Pedal Switch parameter display applied? | Go to Step 15 | Go to Step 8 |
6 |
Does the Stop Lamp Pedal Switch parameter display Released? | Go to Step 7 | Go to Step 10 |
7 |
Does the Stop Lamp Pedal Switch parameter display Applied? | Go to Step 15 | Go to Step 11 |
8 | Test the ignition positive voltage circuit of the stop lamp switch for an open or short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 18 | Go to Step 9 |
9 | Test for an open or short to ground in the TCC brake switch/cruise control release signal circuit of the stop lamp switch. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 18 | Go to Step 14 |
10 | Test the stop lamp switch signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 18 | 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 . Did you find and correct the condition? | Go to Step 18 | Go to Step 13 |
12 | Test the TCC brake switch/cruise control release signal circuit of the stop lamp switch for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 18 | Go to Step 16 |
13 | Test the stop lamp switch signal circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 18 | 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 . Did you find and correct the condition? | Go to Step 18 | Go to Step 16 |
15 | 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 . Did you find and correct the condition? | Go to Step 18 | Go to Step 17 |
16 | Replace the ECM. Refer to Control Module References . Did you complete the replacement? | Go to Step 18 | -- |
17 | Replace the stop lamp switch. Refer to Stop Lamp Switch Replacement . Did you complete the replacement? | Go to Step 18 | -- |
18 |
Does the DTC reset? | Go to Step 2 | System OK |
