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 B1020 00: Auxiliary Electronic Unit (ECU) Performance
DTC B1020 39:: Auxiliary Electronic Unit (ECU) Performance Internal Electronic Failure

### Circuit/System Description

The navigation module performs a self test to detect an internal malfunction.

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

An internal navigation module malfunction exists.

### Action Taken When the DTC Sets

Navigation system fails to operate.

### Reference Information

#### Schematic Reference

Radio/Navigation System Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Navigation 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

### Conditions for Clearing the DTC

• | The condition for setting the DTC is no longer present.

• | A history DTC clears after 50 fault-free ignition cycles.

### Circuit/System Verification

1. Verify DTC B1020 is not set.

⇒ | If the DTC is set, replace the navigation module.

### Repair Instructions

Perform the Diagnostic Repair Verification.

Control Module References for navigation module replacement, setup, and programming.