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.

### DTC Descriptor

DTC U2121: No Communication with Radio Display

### Circuit/System Description

The radio continuously sends a communication signal to the driver information display. Upon receiving the signal, the display sends a reply signal, confirming that it can communicate. The display is directly connects to the radio with no external circuits involved.

### Conditions for Running the DTC

The radio is active.

### Conditions for Setting the DTC

The radio does not receive a response from the radio display for 10 or more consecutive seconds.

### Action Taken When the DTC Sets

The system will set the DTC and disable itself.

### Conditions for Clearing the DTC

• | The current DTC will clear when the radio receives a communication reply from the driver information display.

• | The history DTC will clear after 50 fault-free ignition cycles have occurred.

### Diagnostic Aids

Physically check that the driver information display is correctly mounted to the radio.

### 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 that DTC U2121 is not set.

⇒ | If the DTC is set, replace the driver information display. If the DTC resets, replace the radio.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for radio and driver information display replacement, setup, and programming