Steering Wheel Controls Inoperative Audio/Temp

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

The radio supplies voltage to the audio 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 that is received by the controlled component activating the feature. The temperature up/down switch is part of this circuit, if equipped.

Schematic Reference

Steering Wheel Schematics

Connector End View Reference

Entertainment Connector End Views

Electrical Information Reference

Note: It is Recommend 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 left and right 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 right switch harness connector.

⇒	If less than 8.5 volts test the supply voltage circuit for a short to ground or an 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 circuit test normal, replace the radio.

3. Test for 8.5-10.5 volts between the supply voltage circuit and toggle to the signal circuit at the left and right switch harness connectors.

⇒	If less than 8.5 volts test the signal circuit for an open/ high resistance. If circuit test is normal, replace the radio.

⇒	If greater than 10.5 volts, test the signal circuit for a short to voltage. If the circuit test is normal, replace the radio.

4. Ignition OFF, reconnect the right switch.
5. Ignition ON, Radio ON, test for 8.5-10.5 volts between the supply voltage circuit and signal circuit at the left switch harness connector.

⇒	If less than 8.5 volts test the voltage supply circuit to the left switch for a short to ground or an open/ high resistance. If circuit test normal, refer to component testing.

⇒	If greater than 10.5 volts, repair the voltage supply circuit for a short to B+.

6. Test for 1-4 volts when pressing the right switch between the signal circuit and ground at the left switch harness connector.

⇒	If less than 1-volt, test the signal circuit for a short to ground. If the circuit test is normal, refer to component testing.

7. If circuits test normal, refer to component testing.

Caution: Refer to SIR Caution in the Preface section.

1. Ignition OFF, disconnect the harness connector at the suspect switch.
2. Test the right switch for 2360-2400 ohms of resistance between both remote radio control supply voltage terminals.

⇒	If the resistance is not between 2360-2400 ohms of resistance, replace the faulty switch.

3. Test for infinite resistance between the supply voltage terminal and the signal terminal with the switch in the open position.

⇒	If less than infinite resistance, replace the switch.

4. Test resistance values between the supply voltage terminal and the signal terminal with the switch closed in each position and verify readings are approximate to what the schematic reads.

⇒	If values do not, replace the switch

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Steering Wheel Controls Inoperative Mute

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

The body control module (BCM) supplies voltage to the MUTE switch through the Ignition 1 voltage circuit and monitors the Cellular telephone voice signal circuit. When the switch is pressed the BCM identifies the selection, then sends a serial data message that is received by the component controlled, activating the feature.

Schematic Reference

OnStar Schematics

Connector End View Reference

Electrical Information Reference

Note: It is Recommend 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 MUTE switch.
2. Ignition ON, test for 10-12 volts between the ignition 1 voltage circuit and ground at the switch harness connector.

⇒	If less than 10 volts, test the voltage circuit for short to ground or open/ high resistance. If circuit test normal and the fuse is open, test the signal circuit for a short to ground.

3. Connect testlamp between the signal circuit and ground at the harness connector. Verify testlamp does not illuminate.

⇒	If testlamp illuminates, test the signal circuit for short to voltage. If circuit test normal, replace BCM.

4. Test for 10-12 volts between the voltage circuit and the signal circuit at the harness connector.

⇒	If less than 10 volts, test the signal circuit for an open/high resistance. If the circuit test normal and the fuse is open, test the signal circuit for a short to ground.

5. If all circuits test normal, refer to component testing.

Caution: Refer to SIR Caution in the Preface section.

1. Ignition OFF, disconnect the harness connector at the MUTE switch.
2. Test for infinite resistance between the ignition 1 terminal and the voice signal terminal with the switch in the open position.

⇒	If less than infinite resistance, replace the switch.

3. Test for 0.2-1.5 ohms of resistance between the voltage terminal and the voice signal terminal with the switch closed.

⇒	If resistance is not between 0.2-1.5 ohms, replace faulty switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.