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Radio Controls Malfunction

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/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.

Reference Information

Schematic Reference

Radio/Navigation System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Radio/Audio System Description and Operation

Electrical Information Reference

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

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
  1. Verify no DTCs are set as current.
    2. ⇒If any DTCs are set as current, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  2. Vehicle in Service Mode, radio ON, verify the radio/HVAC controls backlighting illuminates and that all controls perform the correct function.
    3. ⇒If some, but not all, controls operate normally, replace the radio/HVAC control.
    ⇒If all controls are inoperative, refer to Circuit/System Testing.

Circuit/System Testing
  1. Vehicle OFF, disconnect the harness connector at the A20 radio/HVAC controls.
  2. Test for less than 10 Ω between the ground circuit terminal 17 and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Test for less than 20 Ω between the data shield circuit terminal 3 and ground.
    4. ⇒If greater than the specified range, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the A11 radio.
  4. Verify that a test lamp illuminates between the B+ circuit terminal 10 and ground.
    5. ⇒If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  5. Vehicle in Service Mode, test for 2.4-2.75 V between the data circuit terminal 1 and ground.
    6. ⇒If less than the specified range, test the data circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the A11 radio.
    ⇒If greater than the specified range, test the data circuit for a short to voltage. If the circuit tests normal, replace the A11 radio.
  6. Test for 2.4-2.75 V between the data circuit terminal 2 and ground.
    7. ⇒If less than the specified range, test the data circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the A11 radio.
    ⇒If greater than the specified range, test the data circuit for a short to voltage. If the circuit tests normal, replace the A11 radio.
  7. Test for less than 1 V between the wake signal terminal 4 and ground.
    8. ⇒If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the A11 radio.
  8. Test for less than 1 V between the reset signal terminal 15 and ground.
    9. ⇒If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the A11 radio.
  9. Vehicle OFF, reconnect the harness connector at the A20 radio/HVAC controls.
  10. Disconnect the X1 harness connector at the A11 radio.
  11. Install a DMM between wake signal terminal 13 and ground.
  12. Vehicle in Service Mode, verify the DMM reading is 4.5-5.5 V DC.
    13. ⇒If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the A20 radio/HVAC controls.
    ⇒If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the A20 radio/HVAC controls.
  13. Press the power button on the radio controls. Verify the DMM reading is momentarily less than 1 V and returns to 4.5-5.5 V DC each time the power button is pressed
    14. ⇒If not the specified value, replace the A20 radio/HVAC controls.
  14. Test for 4.5-5.5 V between the reset signal terminal 27 and ground.
    15. ⇒If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the A20 radio/HVAC controls.
    ⇒If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the A20 radio/HVAC controls.
  15. If all circuits test normal, replace the A20 radio/HVAC controls and reconnect all harness connectors. Vehicle in Service Mode, radio ON, verify the radio/HVAC controls backlighting illuminates and that all controls perform the correct function If the radio/HVAC controls are still inoperative, replace the A11 radio.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Radio Control Assembly Replacement
    • Control Module References for radio replacement, setup, and programming.
   


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