Lost Communication With Body Control Module (BCM)
The vehicle's computer can't communicate with the BCM.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The vehicle's main computer is trying to talk to the body control module, which handles things like lights and locks, but it's not getting any response, like trying to call someone who won't pick up the phone.
What the computer is actually seeing
The main control unit sends a data signal to the BCM and expects to receive an acknowledgment back within 200 milliseconds. If it doesn't, it sets a U0142 code.
What a healthy reading looks like
BCM should respond within 200 ms. Voltage on the communication line should be around 2.5V during idle and can go up to 5V when active.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect the wiring and connectors between the main computer and the BCM. Look for corrosion or damage.
- 22. Check voltage on the communication line; it should be about 2.5V at rest, going up to 5V when communicating. If it's below 2.0V or floating, diagnose the wiring.
- 33. Verify ground connections at the BCM and main computer. A bad ground can prevent communication.
- 44. Disconnect the BCM and test continuity of the main communication wires to the BCM; look for opens or shorts.
- 55. If all wiring checks out, reconnect the BCM and perform a scan for codes; if codes reappear, the BCM may need replacing.
Common causes
- Damaged or corroded wiring or connectors in the communication pathway.
- Faulty Body Control Module (BCM)
- Poor ground connections near the BCM or main computer.
- Intermittent faults caused by electrical shorts or opens. Midway connections can be faulty.
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's generally drivable, but vehicle functions controlled by the BCM, like interior lights and power locks, may not work.
Will this code come back after resetting?
It can return if the underlying issue isn’t fixed, especially if there's a wiring problem or a faulty BCM.
Why would this code pair with others?
Communication issues often affect multiple systems, so you might see other lost communication codes related to different modules.
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