U0491: Invalid Data Received From Digital Disc Player/Changer Module D
What to do
The car drives entirely normally. This is a disc player in what is almost certainly a rear-seat entertainment system.
Start with whether your car actually has one. These were expensive options, and if any of the entertainment equipment has been replaced with a second-hand unit from a better-equipped car, your car may now be looking for a module it never had. That is a coding correction, not a repair.
If the equipment is fitted and nobody uses it, the advice at U0488 applies: it is still worth dealing with, because a failed module can keep the car's network awake after you lock it and flatten the battery over a few days. Ask whether it can be properly coded out rather than left complaining — that is a reasonable outcome, but it must be done properly rather than by unplugging it.
What this code means
A further disc player module is broadcasting data that cannot be accepted as true. See U0488 for what this family is and why a device nobody uses is still worth attending to.
One numbering note, because the jump looks like an omission. The standard's player C sits in the letter-suffixed part of the U048x range rather than at a decimal number, so the sequence readable here runs A, B and then D.
Four disc player modules on one vehicle effectively means a rear-seat entertainment system with independent screens, each with its own player so that two passengers can watch different things — a configuration found on large vehicles from a particular era and almost nowhere since.
Which makes the question at U0489 the first one here too: is the module fitted? These were expensive options on a shared loom, and infotainment components taken second-hand from a better-equipped vehicle bring its configuration with them. A module the car never had, coded as present, produces this code and nothing to find.
Where the equipment does exist, everything at U0488 applies — the network-awake argument, the water in the boot side panels, and the option of decommissioning a redundant player properly rather than leaving it complaining.
Likely causes
Start here
- Module not coded to the vehicle · specialist
- Corroded or loose connector · easy
- Water ingress into module · moderate
Less common
- Damaged wiring harness · moderate
- Damaged data bus wiring · moderate
- Aftermarket head unit fitted in place of the original · 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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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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