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.

Circuit/System Description

The radio supplies voltage to the steering wheel control momentary contact switches, and monitors the return signal. Each switch is associated to a set resistance value, when pressed a specific voltage drop occurs through a series of resistors unique to that switch. The radio then identifies the switch selected to activate the feature, otherwise sends a serial data message received by the controlled component activating the feature.

Diagnostic Aids

    • Before diagnosis of the steering wheel controls, ensure the primary controls of the associated component are functioning properly.
    • If a single switch function is inoperative, test the suspect switch. Refer to component testing.
    • A poor connection at the right switch could cause all the switches to be inoperative.

Reference Information

Schematic Reference

Steering Wheel Secondary/Configurable Control Schematics

Connector End View Reference

Entertainment/Communication Connector End Views

Description and Operation

Steering Wheel Controls Description and Operation

Electrical Information Reference

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

Circuit/System Testing

Important: It is recommended that Component Testing be performed before Circuit Testing when diagnosing steering wheel controls.

Caution: Refer to SIR Caution in the Preface section.

  1. Ignition OFF, disconnect the harness connector at the right steering wheel control switch.
  2. Ignition ON, radio ON, test for 6.5-9.0 volts between the ignition circuit terminal 5 and ground.
  3. If less than the specified value, test the ignition circuit for a short to ground or open/high resistance. If circuit tests normal, replace the radio.
    If greater than the specified value, test the ignition circuit for short to voltage. If circuit tests normal, replace the radio.
  4. Test for 6.5-9.0 volts between the ignition circuit terminal 5 and the signal circuit terminal 1.
  5. If less than the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the radio.
    If greater than the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the radio.
  6. Install a 3A fused jumper wire between the ignition circuit terminal 5 and the ignition circuit terminal 2.
  7. Disconnect the harness connector at the left steering wheel control switch.
  8. Test for 6.5-9.0 volts between the ignition circuit terminal 4 and ground.
  9. If less than the specified value, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the radio.
    If greater than the specified value, test the ignition circuit for short to voltage. If the circuit tests normal, replace the radio.
  10. Test for 6.5-9.0 volts from the ignition circuit terminal 4 and the signal circuit terminal 1.
  11. If less than the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the radio.
    If greater than the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the radio.
  12. Ignition OFF, disconnect the C1 harness connector at the radio.
  13. Test for infinite resistance between the signal circuit terminal A7 and ground.
  14. If less than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the radio.
  15. If all circuits test normal, test or replace the steering wheel control switch.

Component Testing

Caution: Refer to SIR Caution in the Preface section.

  1. Ignition OFF, disconnect the harness connector at the steering wheel control switches.
  2. Test the right switch for less than 2,400 ohms of resistance between the ignition terminal 5 and the ignition terminal 2.
  3. If greater than the specified value, replace the steering wheel control switch.
  4. Test for infinite resistance between the ignition terminal 5 and the signal terminal 1 with the switch in the open position.
  5. If less than the specified value, replace the steering wheel control switch.
  6. Test for less than 2,400 ohms of resistance between the ignition terminal 5 and the signal terminal 1 with the switch in the closed position.
  7. If greater than the specified value, replace the steering wheel control switch.
  8. Test the left switch for infinite resistance between the ignition terminal 4 and the signal terminal 1 with the switch in the open position.
  9. If greater than the specified value, replace the steering wheel control switch.
  10. Test for less than 12000 ohms of resistance between the ignition terminal 4 and the signal terminal 1 with the switch in the closed position.
  11. If greater than the specified value, replace the steering wheel control switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Steering Wheel Control Switch Assembly Replacement
    •  Control Module References for Radio replacement, setup, and programming