Service Information

Volt

DTC B125A

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 B125A 02: Aerial Signal Circuit Short to Ground

DTC B125A 04: Aerial Signal Circuit Open Circuit

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Radio Aerial Coax	B125A 02	B125A 04	1	--
Ground	--	1	--	--
1. May exhibit possible AM/FM interference.

The AM/FM aerial is part of the multi-band aerial is located on the roof of the vehicle. The radio provides battery voltage to the AM/FM amplifier in the aerial base using the centre conductor of the aerial coaxial cable. When a 12 V signal is seen by the amplifier, both AM and FM signals are amplified.

Conditions for Running the DTC

•	Vehicle in Service Mode.

•	Battery voltage must be between 9-16 V.

Conditions for Setting the DTC

B125A 02

The radio detects a short to ground in the aerial signal circuit centre conductor.

B125A 04

The radio detects an open in the aerial signal circuit centre conductor.

Action Taken When the DTC Sets

Radio reception may be poor or not available.

Conditions for Clearing the DTC

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

•	A history DTC will clears after 50 consecutive malfunction-free ignition cycles have occurred.

Reference Information

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

Vehicle in Service Mode, radio ON, tune to a strong AM or FM station. Verify that the AM or FM reception is clear.

Circuit/System Testing

Vehicle OFF, disconnect the radio aerial coax from the A11 radio and the T4G aerial.
Test for infinite resistance between the aerial coax centre terminal and ground.

⇒	If less than the specified value, replace the aerial coax.

Test for infinite resistance between the coax centre terminal and the outer shield.

⇒	If less than the specified value, replace the aerial coax.

Test for less than 5 Ω on the aerial coax centre circuit from end to end.

⇒	If greater than the specified range, replace the aerial coax.

Vehicle in Service Mode, test for less than 1 V between the aerial coax centre terminal and ground.

⇒	If greater than the specified range, replace the aerial coax.

Connect the aerial coax to the A11 radio. Test for 12-15 V between the aerial coax centre terminal and ground at the T4G aerial connector.

⇒	If not within the specified range, replace the A11 radio.

If all circuits test normal, replace the T4G aerial.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Radio Aerial Base Replacement

•	Control Module References for radio replacement, programming and setup