U0257
Radio Information Display Malfunction - DTC U0257
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 is a separate component from the radio, combined into an assembly. The assembly contains the radio control knobs and buttons for all audio and HVAC functions and the information display. The assembly is supplied battery voltage and ground. The radio uses the wake up circuit to control the power state of the display. The radio controls communicate inputs internally to the display. Display backlighting dimming level, graphical data, and radio control inputs are communicated over the CGI serial data circuits between the display and the radio.
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 - Primary
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 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, test for 2-3 V between the 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 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 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 signal 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 2-3 V
6. Ignition ON.
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 the information display turns on and information is shown on the display.
• If the information display still malfunctions.
Replace the A11 radio.
• If the info display module turns on and information is shown on the display.
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.