GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0568 00: Cruise Control Set Switch Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Cruise Control Switch Signal

1

1

P0567 00 or P0568 00

P0564 00

1. Cruise Control Inoperative / Malfunctioning

Circuit/System Description

The cruise control switch is an input to the engine control module (ECM), while the cruise cancel switch is an input to the body control module (BCM). The ECM monitors the cruise control on/off, set/coast, and the resume/accelerate switch signal circuits in order to detect when a cruise control function switch has been activated. The ECM detects a predetermined voltage signal when a cruise control function switch is applied, with each switch having a different voltage value.

The BCM monitors the cruise cancel switch in order to detect when the cancel switch has been activated. The BCM sends a class 2 message to the ECM regarding the status of the cruise cancel switch.

Conditions for Running the DTC

    • The ignition is ON.
    • The cruise control switch is ON.

Conditions for Setting the DTC

The ECM detects that the resume/accel switch is applied for longer than 90 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.
    • The cruise control system is disabled.

Conditions for Clearing the DTC

    • The DTC becomes history when the conditions for setting the DTC are no longer present.
    • The history DTC clears after 40 malfunction-free warm-up cycles.

Diagnostic Aids

Ensure that the resume/accel switch is not stuck or sticking in the engaged position.

Reference Information

Schematic Reference

Cruise Control Schematics

Connector End View Reference

    •  Cruise Control Connector End Views
    •  Engine Control Module Connector End Views

Description and Operation

Cruise Control Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Scan Tool Data List

Circuit/System Testing

  1. Ignition ON, verify that the Cruise Resume/Accel. Switch parameter reads Active or Invalid.
  2. If the parameter reads Inactive, go to Diagnostic Aids.
  3. Ignition OFF, disconnect the harness connector at the cruise control switch.
  4. Ignition ON, cruise control switch ON, observe the scan tool Cruise Resume/Accel. Switch parameter.
  5. If the scan tool parameter reads Inactive, replace the cruise control switch assembly.
    If the scan tool parameter reads Active or Invalid, test the cruise control switch signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Cruise Control Switch Replacement
    •  Control Module References for ECM replacement, setup, and programming