U0148: Lost Communication With Serial Data Gateway Module C
What to do
Expect a group of features to have stopped — most likely on the specialist or converted part of the vehicle rather than the driving controls.
Three of these translator modules effectively means a van, chassis cab, minibus or motorhome, where a converter has added networks for body equipment, a trailer, a tail-lift, a tachograph or fleet tracking.
If that is your vehicle, contact whoever built or converted the body before a general workshop. That wiring is their work, and the fault is nearly always at the join between their harness and the vehicle's — a corroded splice, an earth on painted metal, a cable rubbing on something that moves. They hold the drawings; a franchised dealer does not.
If it works from cold and fails once warm, or fails over rough ground, say so. Both descriptions point straight at that join.
On an ordinary car, this most likely means the car has been told it has equipment it does not have — which happens after a second-hand module is fitted. That is a coding correction, and there is no fault to find.
The vehicle is normally safe to drive. Do not use any affected body equipment, trailer or lifting gear until it has been checked.
What this code means
A third gateway module has stopped being heard from. See U0146 for what a silent gateway does to everything behind it, and U0449 for where three or more are ordinary.
Three gateways is rare on a passenger car and unremarkable on a commercial one — a chassis cab with a body-builder interface, a bus with a passenger-systems network, a motorhome with a habitation network, a vehicle with auxiliary hydraulics, a tail-lift, or fleet and tachograph equipment on its own bus. Each boundary between those networks is somewhere a gateway sits.
Which makes the first question on a passenger car whether the module exists at all — the U0145 argument, where an exhaustive search finding nothing is itself the answer and the next step is the vehicle's build data.
On a converted vehicle the first question is different and more productive: what did the converter fit, and where does their wiring meet the manufacturer's? These networks are almost always the converter's work rather than the vehicle manufacturer's, and the join between the two harnesses is where these faults live. A spliced connection that has corroded, an earth taken to painted metal, a cable routed against something that moves.
A vehicle that works from cold and fails once warm, or fails over rough ground, is describing that join — and the converter holds the drawings that a franchised workshop does not.
Likely causes
Start here
- Poor wiring splice in an aftermarket installation · moderate
- Module not coded to the vehicle · specialist
- Corroded or loose connector · easy
- Corroded earth connection · moderate
Less common
- Blown fuse or failed supply · easy
- 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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