U0494 Low Generic / SAE

U0494: Invalid Data Received From Digital Audio Control Module A

Network and Communication Invalid Data Received

What to do

If your car has suddenly started sounding different, read this before booking it in for exhaust or suspension work.

The unit this code names is the sound processor in the audio system — and on modern cars it does two things beyond music that most owners have never been told about.

It cancels road noise. Microphones in the roof lining listen to the drone from the road and the engine, and the car plays the opposite of it through the speakers to cancel it out. It does this all the time, whether or not the stereo is on.

And on many cars it plays an engine note into the cabin through the speakers, tuned to the accelerator, because the real engine does not sound the way the makers wanted.

So when this module has a fault, the car can genuinely sound wrong — and that gets blamed on everything else. A new drone or boom at a steady speed gets investigated as a wheel bearing, a tyre or an exhaust. An engine that suddenly sounds coarse or thin gets investigated as an exhaust leak.

Neither is what happened. If this code is stored and a new noise has appeared at the same time, say so before anything is taken apart — it is the cheapest possible explanation and it is very often the right one.

The car is entirely safe to drive.

What this code means

The digital audio control module is broadcasting data that cannot be accepted as true. See U0400 for the family's framing, and U0273 for the same module going silent.

A digital audio module is not an amplifier and not a radio. It is the signal processor between them — the unit that applies the equalisation, delays and crossovers that make a premium sound system sound like one. And on a modern vehicle it is doing two further jobs that have nothing to do with entertainment, which is what makes this code worth more than its severity suggests.

The first is active noise cancellation. Microphones in the headlining pick up the low-frequency drone of the road and the engine, and the module plays an inverted version of it through the speakers, cancelling much of it before it reaches the occupants' ears. It runs whether or not anything is playing.

The second is synthesised engine sound. Many vehicles — particularly small-capacity turbocharged engines and hybrids — play an engine note into the cabin through the speakers, tuned to the throttle and the revs, because the real one does not sound the way the vehicle is meant to.

So a fault in this module makes the car sound wrong, and that is diagnosed as everything except a sound system.

A drone or boom at a steady cruise that was not there before is noise cancellation that has stopped — and it gets investigated as a wheel bearing, an exhaust, a tyre or an engine mount.
An engine that suddenly sounds coarse, thin or unfamiliar is a synthesised note that is no longer being played, and it gets investigated as an exhaust leak or a failing engine.

Both are complete diagnoses that cost nothing, and both are missed because nobody expects a car's noise to come out of its speakers. A stored audio code alongside a new noise complaint is the cheap explanation, and it should be eliminated before anything is dismantled.

Likely causes

Start here

Corroded or loose connector · easy
Aftermarket head unit fitted in place of the original · moderate
Module not coded to the vehicle · specialist

Less common

Damaged wiring under the front seats · moderate
Damaged data bus wiring · moderate
Software updated on one module only · specialist

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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The car — make, model, year and engine. The same fault behaves differently on each.
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