GM Service Manual Online
For 1990-2009 cars only

Diagnostic Fault Information

Important: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

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 selection 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.
    • Review schematic when testing switch resistance values.
    • 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 Schematics

Connector End View Reference

Entertainment Connector End Views

Electrical Information Reference

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

Circuit/System Testing

Note: It is recommended that Component Testing is 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 steering wheel control switches.
  2. Ignition ON, Radio ON, test for 8.5-10.5 volts between the supply voltage circuit and ground at the harness connector.
  3. If less than 8.5 volts test the voltage circuit for short to ground or open/ high resistance. If circuit test normal, replace the radio.
    If greater than 10.5 volts, test the supply voltage circuit for short to voltage. If the circuit test is normal, replace the radio.
  4. Test for 8.5-10.5 volts from the voltage circuit and toggle to the signal circuits at the left and right switch harness connectors.
  5. If less than 8.5 volts, test the signal circuit for an open/ high resistance. If the circuit tests normal, replace the radio.
    If greater than 10.5 volts test the signal circuit for short to voltage. If the circuit test is normal, replace the radio.
  6. Ignition OFF, reconnect the right switch.
  7. Ignition ON, Radio ON, test for 8.5-10.5 volts between the voltage circuit to the left switch and ground at the left switch harness connector.
  8. If less than 8.5 volts, test the voltage circuit for the left switch for a short to ground or open/ high resistance. If the circuit tests normal, refer to component testing.
    If greater than 10.5 volts, test the voltage circuit for the left switch for a short to B+.
  9. Pressing the right switch, test for 1-5 volts between the signal circuit and ground at the left switch harness connector.
  10. If less than 1 volt, test the signal circuit for a short to ground.
  11. If all circuits test normal, test or replace switch.

Component Testing

Caution: Refer to SIR Caution in the Preface section.

  1. Ignition OFF, disconnect the harness connector at the suspect steering wheel control switch.
  2. Test the right switch for 2360-2400 ohms of resistance between the voltage terminal and the voltage terminal for the left switch.
  3. If the resistance is not between 2360-2400 ohms, replace the switch.
  4. Test for infinite resistance between the supply voltage terminal and the signal terminal with the switch in the open position.
  5. If less than infinite resistance, replace the switch.
  6. Test resistance values between the voltage terminal and the signal terminal with the switch closed in each position and verify readings are approximate to what the schematic reads.
  7. If values do not, replace the switch

Repair Instructions

Important: Always 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