|Trouble Code||Fault Location||Probable Cause|
|B1039||Audio [+] output #2 (RF) circuit open||Wiring, Defective or faulty head unit or speaker(s)|
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What Does Code B1039 Mean?
OBD II fault code B1039 is a manufacturer-specific trouble code that is defined by carmaker GM as “Audio [+] output #2 (RF) circuit open”, and is set when the PCM (Powertrain Control Module) or BCM (Body Control Module) detects an open (battery positive output) circuit in the audio system. Note that this code refers specifically to the right front audio circuit.
While this code is largely self-explanatory in the sense that it explains why no audio is coming from the right front of the vehicle, actually finding an fixing the root cause of the problem is sometimes less easy.
For instance, the problem might be as small as a bad electrical contact at any point in the circuit, a poorly crimped terminal, or a blown fuse, the problem could also involve serious issues with the head unit or other communication devices.
In practice, there are no simple solutions to issues like this, except to scan for additional codes and if that does not yield usable diagnostic clues, to trace all (+) circuits with the aid of a proper wiring diagram to locate all connections and relevant ground points. As a practical matter though, the most effective way of testing positive circuits is to verify that output current is present on the correct pin at the head unit, and then to use the voltage drop method to test sections of the relevant wire until the site of the break is found.
Essentially, the voltage drop method involves placing both probes of a digital multi-meter at different points on the same wire, which allows one to measure the drop in current in that section of the wire. While there are other methods to test continuity across connectors and/or slip joints, the voltage drop method is a particularly useful way to measure continuity across joints because results are both immediate and accurate.
Where is the B1039 sensor located?
Note that while a break in continuity could be located almost anywhere in the affected circuit, the most common sites for issues like these are in the first connectors after the head unit, as shown here. Be aware though that you may need access to vehicle-specific tools to remove the head unit from the dashboard without damaging either the dashboard or the head unit.
What are the common causes of code B1039?
Common causes of code B1039 could include one or more of the following-
- Damaged, burnt, shorted, disconnected, or corroded wiring and/or electrical connectors
- Defective or faulty head unit
- Defective or faulty speaker(s)
What are the symptoms of code B1039?
- Stored trouble code
- In some cases, additional codes relating to audio output may be present along with B1039
- Lack of audio from the affected part(s) of the audio system