For 1990-2009 cars

### 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 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 received by the controlled component activating the feature.

### Diagnostic Aids

• | This diagnostic is for the audio steering wheel controls.

• | 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.

### Reference Information

#### Schematic Reference

Steering Wheel Secondary/Configurable Control Schematics

#### Connector End View Reference

• | Entertainment/Communication Connector End Views

• | Secondary/Configurable Control Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

### Circuit/System Testing

Caution: Refer to SIR Caution in the Preface section.

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

1. Ignition OFF, disconnect the harness connector at the audio steering wheel control switch.
2. Ignition ON, Radio ON, test for 8.5-12 volts between the 10-volt reference circuit and ground at the harness connector.

⇒ | If less than 8.5 volts, test 10-volt reference circuit for short to ground or open/high resistance. If the circuit test is normal, replace the radio.

3. Test for 0-0.5 volts between the signal circuit and ground at the harness connector.

⇒ | If greater than 0.5 volt, test the signal circuit for a short to voltage. If the circuit test is normal, replace the radio.

4. Test for 8.5-12 volts between the supply voltage circuit and the signal circuit at the harness connector.

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

5. Ignition OFF, disconnect the harness connector at the radio.
6. Test for infinite resistance between the signal circuit and ground at the harness connector.

⇒ | If less than infinite ohms of resistance, test the signal circuit for a short to ground. If the circuit test is normal, refer to component testing.

7. If all circuit test normal, refer to component testing.

### Component Testing

Caution: Refer to SIR Caution in the Preface section.

1. Ignition OFF, disconnect the harness connector at the audio steering wheel control switch.
2. Test for infinite resistance between the 10-volt reference terminal and the signal terminal with the switch in the open position.

⇒ | If less than infinite resistance, replace the switch.

3. Test resistance values between the 10-volt reference 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.

### 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