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For 1990-2009 cars only

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

Go to Diagnostic System Check - Vehicle

2

  1. Turn OFF the ignition.
  2. Disconnect the stop lamp switch.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the stop lamp switch signal circuit and a good ground.

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

  1. Use a scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC.

Does the DTC reset?

Go to Step 2

System OK