DTC P0571 7.8L
Circuit Description
The torque converter clutch (TCC) brake switch/cruise control release signal circuit is incorporated into the stop lamp switch. The TCC brake switch/cruise control release signal circuit portion of the stop lamp switch is a normally closed switch. The stop lamp switch signal circuit portion of the stop lamp switch is a normally open switch. When the brake pedal is released, the engine control module (ECM) detects a high voltage signal on the TCC brake switch/cruise control release signal circuit and a low signal voltage signal on the stop lamp switch signal circuit.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0571 (7.8L) Cruise Control Brake Switch Circuit
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The traction control system (TCS) or the antilock brake system (ABS) have not failed. |
Conditions for Setting the DTC
| • | When the brake pedal is released, the ECM detects a high voltage signal on the stop lamp switch signal circuit or when the ECM detects a low voltage signal on the TCC brake switch/cruise control release signal circuit. |
| • | The above conditions are present for 1.5 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
| • | Refer to Exterior Lighting Systems Description and Operation in order to avoid a misdiagnosis. |
| • | For an intermittent, refer to Testing for Intermittent Conditions and Poor Connections . |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Cruise Control Schematics Connector End View Reference: Lighting Systems Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Does the test lamp illuminate? | Go to Step 3 | Go to Step 4 |
3 | 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 9 | Go to Step 6 |
4 | Test the torque converter clutch (TCC) brake switch/cruise control release signal circuit for an open or for a high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 9 | Go to Step 5 |
5 | 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 9 | Go to Step 7 |
6 | 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 9 | Go to Step 8 |
7 | Replace the stop lamp switch. Refer to Stop Lamp Switch Replacement . Did you complete the repair? | Go to Step 9 | -- |
8 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 9 | -- |
9 |
Does the DTC reset? | Go to Step 2 | System OK |
