GM/Detroit 6.5L ENGINE CONTROLS – DTC P0571 Cruise Control Brake Switch Circuit

Circuit Description
The TCC normally closed cruise brake switch supplies a B+ signal on the Brake Switch Input circuit to the PCM. The circuit is opened when the brakes are applied. The stop lamp/cruise control normally open brake switch supplies a B+ signal on the Stoplamp Switch Input circuit to the PCM when the brake is applied.

Conditions for Running the DTC
• Brake switches disagree for 10 consecutive minutes.
or
• TCC and cruise control brake switches are not toggling open and closed, during 6 brake applications on the same ignition cycle.

Conditions for Setting the DTC
• Brake switches disagree for 10 consecutive minutes.
or
• TCC and cruise control brake switches are not toggling open and closed, during 6 brake applications on the same ignition cycle.

Action Taken When the DTC Sets
• The PCM disallows all cruise control inputs.
• TCC shift schedules may be affected.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
• The PCM records the operating conditions at the time the diagnostic fails. This information stores in the Failure Records.

Conditions for Clearing the MIL/DTC
• A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures
• The use of a scan tool.

Diagnostic Aids
Refer to PCM Intermittent Diagnostic Trouble Codes or Performance. Check customer driving habits and/or unusual traffic conditions (i.e. stop and go, expressway traffic).

Test Description
Number(s) below refer to the step nurnber(s) on the Diagnostic Table.
4. This test checks the feed circuit.
6. This test simulates brake switch closed or brakes ON.

 

 

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