U0491 code meaning
Invalid Data Received From Digital Disc Player/Changer Module D
What U0491 means
U0491 belongs to a fourth networked disc player or changer, module D: frames from that drive still arrive, yet the radio or gateway rejects their content. Its lost-contact partner is U0190; drives A to C have U0488, U0489 and U048A. Separate disc drives did exist, for example the media disc player in GM's 2017 Silverado, Sierra, Suburban, Tahoe and Yukon with entertainment package, which bulletin 17-NA-378 replaced when film sound drifted out of sync with the picture. A fourth unit of this kind is practically unknown, and no manufacturer documents U0491 or publicly assigns the letter D. On a car without such a drive the code hints at coding or software rather than hardware. No MIL; at most disc playback is lost.
U0491 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.3 to 1.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0491
- Discs in that drive cannot be played
- Code stored without noticeable fault on cars lacking such a drive
Common causes of U0491
- PossibleVehicle coding or head-unit software expecting a fourth disc drive that is absent or different
- PossibleDisc drive D hung up or internally faulty
- Less likelyPoor supply, ground or bus link at the drive
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Disc changer module d
What each part of U0491 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 91 | The exact fault in that area. |
What to do next
- Note U0491 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U0491
What does U0491 mean?
U0491 means "Invalid Data Received From Digital Disc Player/Changer Module D". U0491 belongs to a fourth networked disc player or changer, module D: frames from that drive still arrive, yet the radio or gateway rejects their content. It is a generic code, so it means the same on every make.
Is it safe to drive with U0491?
U0491 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U0491 fail an emissions test?
U0491 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U0491 to fix?
Difficulty: medium. A typical repair takes 0.3 to 1.5 hours of work. This is a job for a workshop.
Will U0491 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.