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 Descriptors

DTC B1287 01: Amplifier Control Signal Circuit Short to Battery
DTC B1287 02: Amplifier Control Signal Circuit Short to Ground
DTC B1287 04: Amplifier Control Signal Circuit Signal Open

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Amplifier Control | B1287 02 | B1287 04 | B1287 01 | --

### Circuit/System Description

The radio provides a remote amplifier mute output circuit to control overall muting of the remote amplifier. The amplifier receives pulse width modulated (PWM) signals on the control circuit at varying duty cycle percentages for controlling muted and unmuted functions of the amplifier. Circuitry internal to the radio monitors the remote amplifier mute circuit for faults and sets the appropriate DTC when faults are detected.

### Conditions for Running the DTC

• | Radio ON.

• | Battery voltage must be between 9-16 volts.

### Conditions for Setting the DTC

The DTC will set when the radio detects a short to voltage, short to ground, or an open/high resistance in the amp mute circuit.

### Action Taken When the DTC Sets

Audio amplifier functions are disabled.

### Conditions for Clearing the DTC

• | The condition responsible for setting the DTC no longer exists.

• | A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

### 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 Testing

1. Ignition OFF, disconnect the X3 harness connector at the audio amplifier.
2. Ignition ON, radio ON and un-muted, test for 0.5 -1.0 volts between the signal circuit terminal 16 and ground.

⇒ | If greater than the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the radio.

⇒ | If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the radio.

3. If all circuits test normal, replace the audio amplifier.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for Audio Amplifier and Radio replacement, setup, and programming