U0445: Invalid Data Received From Body Control Module D
What to do
Before driving anywhere, have somebody stand behind the car while you use the brakes, the indicators and the lights.
On most cars this code names the computer at the back, which runs the rear lights, the rear wiper, the heated rear screen and the boot lock. The reason to check is that you cannot see any of that from the driver's seat, and driving with no brake lights is genuinely dangerous rather than merely inconvenient.
Then look under the boot floor, where the spare wheel lives. These modules sit in the wettest part of the car, and standing water there — from an aged tailgate seal, a blocked drain channel, or a rear light cluster whose gasket has hardened — is the commonest reason for this fault by a wide margin. Finding water is more useful than any test, and drying and sealing it is the actual repair.
Otherwise the car is normally safe to drive in daylight.
What this code means
A body control module is broadcasting data that cannot be accepted as true. See U0443 for why these modules are lettered and what that implies about where to look.
On most vehicles carrying this many body modules, D is at the back, and the rear zone is worth a paragraph of its own because of what it runs and where it lives.
A rear or tailgate module typically operates the light clusters, the number plate lamps, the rear wiper and washer, the heated rear screen, the boot or tailgate lock and, on a powered tailgate, its motor and pinch protection. So a single fault here takes out a set of things that look entirely unrelated to each other and are all, in fact, at the same end of the car.
It also lives in the wettest structural part of the vehicle. Tailgate seals age, drain channels block with leaf litter, and a rear light cluster whose gasket has hardened lets water into the boot floor rather than outside it. Lift the boot floor and look under the spare wheel before anything is condemned — standing water there explains this code and a great deal else.
One safety point deserves stating. Where the affected zone runs the rear lighting, the vehicle may be driving with no brake lights or no indicators at the back while everything looks normal from the driver's seat. That is a real hazard rather than an inconvenience, and it is checkable in a minute with somebody standing behind the car.
Likely causes
Start here
- Water ingress into module · moderate
- Corroded or loose connector · easy
- Damaged wiring harness · moderate
Less common
- Broken wire in the door harness boot · moderate
- Faulty body control module · specialist
- Damaged data bus wiring · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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