Radio Controls Malfunction
Radio Controls Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The radio/HVAC controls are supplied battery voltage and ground. The radio controls the power state of the controls via a wake up circuit. Communications between the radio controls and the radio are through the CGI serial data circuits.
Communications between the HVAC controls and the HVAC control module are on a separate LIN circuit. The HVAC control module communicates status information to the radio via GMLAN for HVAC information display.
Reference Information
Schematic Reference
Radio/Navigation System Schematics Radio/Navigation System Schematics
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Radio/Audio System Description and Operation Radio/Audio System
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON, A11 radio ON.
2. Verify that all radio controls operate and perform the correct function.
• If some, but not all, controls operate normally.
Replace the A20 radio/HVAC controls.
• If all controls are inoperative.
Refer to Circuit/System Testing
• If all radio controls operate and perform the correct function.
3. All OK.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the A20 radio/HVAC controls.
2. Test for less than 10 ohms between the ground circuit terminal 17 and ground.
• If 10 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 10 ohms
3. Test for less than 20 ohms between the data shield circuit terminal 3 and ground.
• If 20 ohms or greater
1. Ignition OFF, disconnect the X1 connector at the A11 radio.
2. Test for less than 2 ohms in the data shield circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the A11 radio.
• If less than 20 ohms
4. Verify that a test lamp illuminates between the B+ circuit terminal 10 and ground.
• If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF.
2. Test for less than 2 ohms in the B+ circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, refer to Power Mode Mismatch Power Mode Mismatch.
• If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF.
2. Test for infinite resistance between the B+ circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the A20 radio/HVAC controls.
• If the test lamp illuminates.
5. Ignition ON.
6. Test for 2-3 V between the serial data circuit terminals listed below and ground.
* terminal 1
* terminal 2
• If less than 2 V
1. Ignition OFF, disconnect the X1 harness connector at the A11 radio.
2. Test for infinite resistance between the serial data circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the serial data circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the A11 radio.
• If greater than 3 V
1. Ignition OFF, disconnect the X1 harness connector at the A11 radio. Ignition ON.
2. Test for less than 1 V between the serial data circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the A11 radio.
• If between 2-3 V
7. Test for less than 1 V between the control circuit terminals listed below and ground.
* terminal 4
* terminal 15
• If greater than 1 V
1. Ignition OFF, disconnect the X1 harness connector at the A11 radio. Ignition ON.
2. Test for less than 1 V between the control circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the A11 radio.
• If less than 1 V
8. Ignition OFF, disconnect the X1 harness connector at the A11 radio.
9. Test for infinite resistance between the control circuit terminals listed below and ground.
* A20 radio/HVAC controls terminal 4
* A20 radio/HVAC controls terminal 15
• If less than infinite resistance,
Repair the short to ground on the circuit.
• If infinite resistance
10. Test for less than 2 ohms between the control circuits listed below.
* A20 radio/HVAC controls terminal 4 and the A11 radio terminal 13 X1
* A20 radio/HVAC controls terminal 15 and the A11 radio terminal 27 X1
• If 2 ohms or greater
Repair the open/high resistance in the circuit.
• If less than 2 ohms.
11. Replace the A20 radio/HVAC controls. Connect all harness connectors.
12. Ignition ON, radio ON.
13. Verify that all radio controls operate and perform the correct function.
• If the radio controls still malfunction.
Replace the A11 radio.
• If all radio controls operate and perform the correct function.
14. All OK
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Radio Control Assembly Replacement Radio Control Assembly Replacement
* Control Module References Control Module References for radio replacement, programming, and setup.