U055D: Invalid Data Received From Special Purpose Vehicle Control Module D
What to do
The vehicle drives normally. This code covers equipment fitted for the vehicle's job — beacons, a tail lift, refrigeration, body power, a wheelchair ramp — rather than anything the car maker built.
Go to whoever converted or fitted out the vehicle, not the vehicle dealer. The fault is nearly always at the join between their installation and the base vehicle's wiring, and they designed that join.
If the vehicle stands over a weekend and the battery is flat on Monday, say so first. Added equipment that keeps the vehicle awake is the commonest real fault here, and it is an installation problem with a straightforward fix.
If this is an ordinary car and none of the above applies, then something fitted to it has come from an ex-fleet or ex-emergency vehicle and brought its configuration along. Nothing is broken — it needs coding to match the car it is now in.
What this code means
Special purpose vehicle control module D is broadcasting data that cannot be accepted as true. See U0400 for what an invalid-data code is and why the module it names is usually the messenger rather than the culprit.
The letter narrows the fault to one instance of a repeated module, and that is genuinely useful — but it does not say which one physically. The mapping from letter to position is the manufacturer's choice and differs between makes, so only the vehicle's own documentation resolves it.
Two consequences. Several letters stored together means the fault is upstream of all of them — a shared supply, a shared earth, or the bus. Exactly one letter stored is the more informative case: the others are working, so everything they share is proven good.
"Special purpose vehicle" is the standard's name for equipment fitted to a vehicle built or converted for a job, and understanding that is most of the diagnosis.
These are ambulances, fire appliances, police vehicles, recovery trucks, refrigerated vans, tippers, mobile workshops, wheelchair-accessible conversions and motorhomes. The modules control the equipment that makes the vehicle useful — beacons and sirens, tail lifts and ramps, body power, refrigeration, PTO-driven machinery, auxiliary batteries.
Four letters means four such modules, which is normal on a purpose-built vehicle and unheard-of on a private car.
So the first question is which vehicle you are actually looking at. On a converted vehicle, the equipment was installed by a body builder or converter rather than the vehicle manufacturer, and the join between their wiring and the chassis is where these faults live. The dealer who sold the chassis is frequently the wrong place to take it.
On an ordinary car this code means something else entirely: a second-hand module from an ex-fleet or ex-emergency vehicle, still carrying its donor's configuration. Nothing is broken; the coding describes a vehicle this is not.
Auxiliary electrics are the classic cause on working vehicles, because converter installations routinely add loads that keep the base vehicle awake — and a van that will not sleep is a van with a flat battery on Monday.
Likely causes
Start here
- Poor wiring splice in an aftermarket installation · moderate
- Module not coded to the vehicle · specialist
- Corroded or loose connector · easy
Less common
- Second hand module locked to another vehicle · specialist
- Another module holding the bus down · 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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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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