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. |
Circuit/System Description
The cruise control switch is an input to the body control module (BCM). The BCM monitors the cruise control on/off, set/coast, resume/accelerate, and cancel switch signal circuits in order to detect when a cruise control function switch has been activated. The BCM detects a predetermined voltage signal when a cruise control function switch is applied, with each switch having a different voltage value. The BCM sends a GMLAN serial data message to the ECM indicating the status of the cruise control switches.
Conditions for Enabling Cruise Control
| • | The vehicle speed is greater than 40 km/h (25 mph). |
| • | The vehicle is not in PARK, REVERSE, NEUTRAL, or 1st gear. |
| • | The system voltage is within 9-16 volts. |
| • | The brakes or park brake is not applied. |
Diagnostic Aids
Caution: Refer to SIR Caution in the Preface section.
| • | Disable the inflatable restraint steering wheel module when performing this diagnostic table. Refer to SIR Disabling and Enabling . |
| • | In order to avoid misdiagnosis, inspect for proper operation of the brake lamps. Refer to Exterior Lighting Systems Description and Operation . |
| • | Electromagnetic interference (EMI) on the speed sensor signal circuit may cause erratic cruise control operation. |
| • | For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections . |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Circuit/System Verification
| • | Ensure that the following cruise control switches are not stuck in the engaged position: |
| - | ON/OFF switch |
| - | - Set switch |
| - | + RES switch |
| - | Cancel switch |
| • | Inspect for proper operation of the stop lamps. Refer to Exterior Lighting Systems Description and Operation . |
| • | Rotate the steering wheel to both steering stops while activating each cruise control switch separately. With a scan tool, observe the Cruise Control Switch and the Cruise Cancel Switch parameters in the BCM. Ensure that each cruise control switch activated and that each displayed switch position in the Cruise Control Switch and Cruise Cancel Switch parameters do not match as the steering wheel is turned. |
| ⇒ | If the parameters match with each depressed switch accordingly, replace the ECM. |
Circuit/System Testing
Caution: Refer to SIR Caution in the Preface section.
Disable the inflatable restraint steering wheel module when performing this diagnostic. Refer to SIR Disabling and Enabling .
- Ignition OFF, remove the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement .
- Disconnect the harness connector of the cruise control switch.
- Ignition ON, measure for 10 volts or greater at the cruise control supply voltage circuit.
- Ignition OFF, test for an open, a high resistance, a short to ground, or a short to voltage in the cruise control switch signal circuit.
- Test the component. If the circuits and the component tests are normal, replace the BCM.
| ⇒ | If less than 10 volts, check for an open/high resistance or for a short to ground on the cruise control supply voltage circuit. |
Component Testing
Caution: Refer to SIR Caution in the Preface section.
Disable the inflatable restraint steering wheel module when performing this diagnostic. Refer to SIR Disabling and Enabling .
Important: The cruise control ON/OFF switch must be ON in order to properly measure the resistance of the - SET, the + RES, and the Cancel switches.
- Ignition OFF, remove the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement .
- Disconnect the harness connector at the cruise control switch.
- Cruise control switch ON, measure the resistance between terminals 4 and 5 at 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 on the schematic for the ON/OFF, - SET, and the + RES.
- Cruise control switch ON, measure the resistance between terminals 4 and 6 at the cruise control switch side of the connector. Activate and deactivate the cancel switch.
| ⇒ | If any of the resistance measurements for the OFF, ON, - SET, and + RES are not within the listed resistance values, replace the cruise control switch assembly. |
| ⇒ | If the resistance does not show continuity when activated and open when deactivated, replace the cruise control switch assembly. |
Function Switch | Minimum Resistance Value | Maximum Resistance Value |
|---|---|---|
OFF | O.L. | O.L. |
ON | 6.5K ohms | 7.0K ohms |
- SET | 2.2K ohms | 2.4K ohms |
+ RES | 3.7K ohms | 3.8K ohms |
Cancel | 0.0K ohms | 0.5K ohms |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM or ECM replacement, setup, and programming |
