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 Open

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Amplifier Control | DTC B1287 02,** | DTC B1287 04,** | DTC B1287 01,* | --
* No audio output. ** 4 Channel unmute, possible noise in speakers when radio muted or turned off

### Circuit/System Description

The radio amplifier control circuit provides varying pulse width modulated (PWM) signals to control overall muting of the amplifier. The PWM signals are varying duty cycle percentages ranging from 0-100 percent. A low duty cycle unmutes all amplifier channels and a high duty cycle mutes all amplifier channels. The radio monitors the amp control circuit for faults. When a fault is detected the radio sets the appropriate DTC.

### Conditions for Running the DTC

The following are conditions that must be present in order for the radio to enable the diagnostics.

• | The radio is in ACCESSORY, RUN, or RAP power mode.

• | The system voltage is at least 9 volts and no more than 16 volts.

### Conditions for Setting the DTC

The radio detects a fault on the Amplifier Control circuit 400 ms after radio activates the Remote Enable circuit.

### Action Taken When the DTC Sets

Radio sets the DTC and continues to output correct state.

### Conditions for Clearing the DTC

• | The condition must be corrected.

• | A history DTC clears after 100 malfunction-free ignition cycles.

• | The radio receives the clear code command from the scan tool.

### 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

Verify the audio system performance by adjusting the fade and balance of the speaker outputs.

### Circuit/System Testing

#### RPO Code UQA

1. Ignition OFF, disconnect the X1 harness connector at the A11 radio.
2. Ignition ON, test for less than 1 V between the radio audio mute signal terminal 37 and ground.

⇒ | If greater than the specified value, test the circuit for a short to voltage. If the circuit tests normal, replace the T3 amplifier.

3. Ignition OFF, test for greater than 20 Ω between the radio audio mute signal terminal 37 and ground.

⇒ | If less than the specified value, test the circuit for a short to ground. If the circuit tests normal, replace the T3 amplifier.

4. Ignition OFF, disconnect the X3 harness connector at the T3 amplifier.
5. Test for less than 5 Ω between the radio X1 terminal 37 to the amplifier X3 terminal 6.

⇒ | If greater than specified range, test the circuit for an open/high resistance.

6. If all circuits test normal, replace the A11 radio.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for radio and amplifier replacement, setup, and programming