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 B1259 02: Antenna Ground Circuit Short to Ground

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
B+ Voltage | -- | 1 | -- | --
Left Audio Signal (+) | 2 | 2 | 2 | --
Left Audio Signal (-) | 2 | 2 | 2 | --
Right Audio Signal (+) | 3 | 3 | 3 | --
Right Audio Signal (-) | 3 | 3 | 3 | --
Digital Radio Antenna Coax | B1259 02 | 4 | 4 | --
Ground | -- | 1 | -- | --
1. No communication with Digital Audio Broadcast module. 2. No or distorted audio from left side speakers when listening to digital radio. 3. No or distorted audio from right side speakers when listening to digital radio. 4. Poor or no reception with Digital Audio Broadcast.

### Circuit/System Description

The Digital Audio Broadcast (DAB) radio receiver receives a digital radio signal via the digital radio antenna. This signal is passed to the DAB module through the digital radio antenna coax. The DAB module sends a varying AC mV signal through separate left and right audio circuits (+ and -) to the radio. The voltage amount and rate of change is dependent upon the type of signal being received. The radio then processes these signals and passes the audio to the amplifier.

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

#### B1259 02

The Digital Audio Broadcast module detects a short to ground in the antenna circuit.

### Action Taken When the DTC Sets

The radio no longer emits audio when on digital audio broadcast radio.

### Conditions for Clearing the DTC

• | A current DTC will clear when the conditions for setting the DTC are no longer present.

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

### Diagnostic Aids

When diagnosing digital radio concerns, the vehicle should be located outside with an unobstructed view of the sky to ensure proper reception of the digital radio signal. Reception may limited, intermittent or not possible inside structures or under heavy cover.

### 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

#### Special Tools

EL-48028 Digital Radio Test Antenna

### Circuit/System Verification

1. Tune to a strong AM or FM station and verify each speaker is producing clear and even sound, with no distortion.

⇒ | If any speaker is not producing sound or the sound produced is distorted, refer to Speaker Malfunction.

2. With the vehicle outside in an area with an unobstructed view of the sky, tune to Digital Audio. Verify reception is clear and audio is emitted from the A11 radio.

### Circuit/System Testing

1. Ignition OFF, disconnect the digital audio antenna coax from the digital audio broadcast module. Connect the EL-48028 to the radio.
2. Radio ON, tuned to Digital Audio, verify DTC B1259 is not set as current.

⇒ | If the DTC is current, replace the A12 digital radio receiver.

3. Ignition OFF, reconnect the antenna coax to the radio, disconnect the digital radio antenna coax from the T4H digital radio antenna.
4. Ignition ON, test for 4.5-5.5 V between the antenna coax center terminal and the coax outer shield.

⇒ | If not within the specified range, replace the antenna coax.

5. If all circuits test normal, replace the T4H digital radio antenna.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for Radio and Digital Audio Broadcast replacement, setup, and programming