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 and resume/accelerate switch signal circuit 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 engine control module (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 park brake or brakes are not applied. |
Diagnostic Aids
Caution: Refer to SIR Caution in the Preface section.
Important: Repair any brake system related symptoms and DTCs before performing this diagnostic.
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 the following:
| • | Ensure that the following cruise control switches are not stuck in the engaged position: |
| - | On/Off switch |
| - | Set/Coast switch |
| - | Resume/Accel switch |
| • | With the Cruise On/Off Switch ON, rotate the steering wheel to both steering stops while activating each cruise control switch separately. With a scan tool, observe the Cruise Set/Coast Switch and the Cruise Resume/Accel Switch parameters in the ECM and the Cruise Control Switch parameter in the BCM. Ensure that each cruise control switch activates and that each displayed switch position parameters match, as the steering wheel is turned. |
| • | Inspect for proper operation of the stop lamps and the braking system. 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
Scan Tool Reference
Circuit/System Verification
Important: The cruise on/off switch must be ON in order to view all of the cruise control parameters properly.
Ignition ON, observe the scan tool Cruise Control Switch parameter in the BCM while pressing the various cruise control switches. The reading should be Error.
| ⇒ | If the Cruise Control Switch parameter toggles between On, Off, Resume and Set accordingly with the depressed switches, then replace the ECM. |
Circuit/System Testing
Caution: Refer to SIR Caution in the Preface section.
Important: Repair any brake system related symptoms and DTCs before performing this diagnostic.
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 at the steering wheel controls - left.
- Ignition ON, measure for B+ at the EPS/STR WHL CNTRL supply voltage circuit.
- Ignition OFF, disconnect the harness connector C2 of the BCM.
- Install a fused jumper at the harness connector of the steering wheel controls switch - left between the EPS/STR WHL CNTRL supply voltage circuit terminal 4 and the cruise control switch signal circuit terminal 6.
- Ignition ON, verify that a test lamp illuminates at the harness connector of the BCM C2 between the cruise control switch signal circuit terminal 61 and ground.
- Ignition OFF, disconnect the fused jumper.
- Ignition OFF, verify that the test lamp does not illuminate at the harness connector of the BCM C2 between the cruise control switch signal circuit terminal 61 and ground.
- If the circuits test normal, test the component. If the component tests normal, replace the BCM.
| ⇒ | If less than the specified value, check for a short to ground or an open/high resistance on the EPS/STR WHL CNTRL supply voltage circuit. |
| ⇒ | If the test lamp does not illuminate, test the cruise control switch signal circuit for a short to ground or an open/high resistance. |
| ⇒ | If the test lamp illuminates, test the cruise control switch signal circuit for a short to voltage. |
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 .
- Ignition OFF, remove the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement .
- Ignition OFF, disconnect the harness connector at the steering wheel controls - left.
- Measure the resistance between terminals 4 and 6 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 for the On, Off, - SET and the + RES switches.
| ⇒ | If any of the resistance measurements for the On, Off, - SET, and the + RES switches are not within the listed resistance values, replace the steering wheel controls - left. |
Function Switch | Minimum Resistance Value | Maximum Resistance Value |
|---|---|---|
Off | O.L. | O.L. |
On | 7.8k Ohms | 8.6k Ohms |
- SET | 1.2k Ohms | 1.3k Ohms |
+ RES | 2.7k Ohms | 3.0k Ohms |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM or ECM replacement, setup, and programming |
