Body Control Module (BCM) Failure
The Body Control Module has detected a fault.
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 Body Control Module, which runs things like lights and windows, is having a problem communicating or operating correctly.
What the computer is actually seeing
The BCM monitors various inputs and outputs; when it senses failure in its internal circuits or loses power, it generates a B1620 code.
What a healthy reading looks like
BCM should have powered input voltage of 12-14V; internal resistance checks should show continuity without irregular spikes.
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. Visually inspect the wiring and connectors to the BCM for corrosion or damage. Are there visible issues? If yes, repair the wiring or connectors. Proceed to step 5.
- 22. Check the battery voltage. Is it between 12-14V with accessories off? If no, rectify the voltage issue before further diagnostics.
- 33. Clear the code and perform a reset. Does the code return immediately? If yes, the BCM may be faulty.
- 44. Test the BCM with a scan tool for any other codes and check for functionality of controls (e.g., lights, locks). Are they functioning normally? If not, suspect a BCM failure.
- 55. Replace the BCM if all other diagnostics point to its failure.
Common causes
- Corroded or damaged wiring to the BCM
- Faulty BCM
- Low battery voltage or poor grounding
- Disconnects or connectors issue
- Moisture intrusion in the BCM housing
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It may be safe, but you'll lose function of lights and locks; address it soon.
Will the code come back?
If the BCM is faulty, it likely will return after clearing—replace it.
Why does this code appear with others?
It often pairs with other BCM-related codes, indicating a broader issue with the module.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
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