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.

Diagnostic Fault Information

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Signal Performance

B+

1

P0564

1

--

P0564

Cruise Control ON/OFF Switch Signal

1

P0564

1

P0567

P0568

P0564

Cruise Control Resume/Accel. Switch Signal

1

1

1

P0567

--

Cruise Control Set/Coast Switch Signal

1

1

1

P0568

--

1. Cruise Control Malfunction

Circuit/System Description

The cruise control switch is an input to the engine control module (ECM). The ECM monitors the cruise control switch signal circuit in order to detect when a cruise control function has been requested. The ECM detects a specific voltage signal on the cruise control switch signal circuit when a cruise control function switch is activated, with each switch having a different predetermined voltage value.

Reference Information

Schematic Reference

Cruise Control Schematics

Connector End View Reference

Component 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

Control Module References for scan tool information

Circuit/System Verification

Engine ON, while rotating the steering wheel to both steering stops, observe the scan tool Cruise Control Switch parameter while pressing each of the cruise control switches. The parameter should toggle between ON, OFF, Resume, Set, and Cancel as the applicable switch is pressed.

Circuit/System Testing

  1. Ignition OFF, disconnect the X204 harness connector at the turn signal/multifunction switch.
  2. Ignition ON, test for B+ between the B+ circuit terminal A8 and ground.
  3. If less than the specified value, test the circuit for a short to ground or an open/high resistance.
  4. Verify the scan tool Cruise ON/OFF switch parameter displays OFF.
  5. If not the specified value, test the signal circuit terminal B8 for a short to voltage. If the circuit tests normal, replace the ECM.
  6. Install a 3A fused jumper wire between the signal circuit terminal B8 and the B+ circuit terminal A8. Verify the scan tool Cruise ON/OFF Switch parameter displays ON.
  7. If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
  8. If all circuits test normal, test or replace the turn signal/multifunction switch.

Component Testing

  1. Ignition OFF, disconnect the X204 steering column harness connector.
  2. Ignition ON, cruise control switch ON, measure the resistance between terminals A8 and B8 on the cruise control switch side of the connector. Individually activate and hold each cruise control function switch and compare the resistance reading to the values in the table for the appropriate switch.
  3. If any resistance measurements for any of the switches are not within the listed resistance values, replace the turn signal/malfunction switch.

Function Switch

Minimum Resistance Value

Maximum Resistance Value

OFF

O.L.

O.L.

ON

7.8k Ohms

8.6k Ohms

Set/Coast

1.2k Ohms

1.3k Ohms

Resume/Accel.

2.7k Ohms

3.0k Ohms

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Turn Signal Multifunction Switch Replacement
    •  Control Module References for ECM replacement, setup, and programming