U015C: Lost Communication With Automated Driving System Control Module A
What to do
Assume you have none of the driver assistance systems, and drive accordingly. Adaptive cruise, lane keeping and automatic emergency braking will not intervene. The car itself is unaffected — steering, brakes and engine are exactly as they were — but anything that watched the road for you has stopped.
That habit is the real hazard. These systems become invisible when they work, so the useful thing is to consciously go back to your own following distance for the rest of the journey.
Mention any of these, because they are the common causes: a recent windscreen replacement, any front-end repair or bumper work, or a low-speed knock while parking — even one that left no visible damage.
If a camera or radar is replaced or disturbed, insist it is recalibrated. An uncalibrated sensor is worse than a switched-off one, because the system still operates while aiming at the wrong part of the road.
What this code means
The module running the vehicle's driver assistance and automated driving functions has stopped being heard from. The family's framing is at U0100.
The design intent here is worth stating first, because it is reassuring and it is also the risk. A vehicle that loses this module reverts to being an ordinary car — the steering, brakes and engine are unchanged and entirely under the driver's control. Nothing is taken away that the car did not add.
The risk is the habit. Adaptive cruise control, lane centring and automatic emergency braking are systems people stop consciously noticing, and a driver who has learned that the car maintains its own distance is a driver who has stopped checking. When those functions vanish, the warning is a symbol on a dashboard that is now full of them.
So the practical advice is behavioural rather than mechanical: drive as though the car has none of it, because it has none of it.
As for where the fault is, this module is unusually exposed to ordinary events. It depends on a camera behind the windscreen and one or more radars behind the bumper, and windscreen replacement, front-end repair, a low-speed parking knock and even a heavy bumper wash reach its hardware. Its own supply and network wiring run to a module that is often mounted behind the dashboard or the front bumper beam.
Anything replaced here needs calibrating, and that is not optional or a formality. A camera or radar that has been disturbed and not recalibrated aims at a different part of the road than the module believes — which is worse than the system being off, because it works and it is wrong.
Likely causes
Start here
- Corroded or loose connector · easy
- Damaged data bus wiring · moderate
- Failed power or earth supply to the module · moderate
Less common
- Radar sensor not calibrated after front-end work · specialist
- Damaged wiring harness · moderate
Symptoms
Components involved
Information, not instruction
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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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