U1121Data bus: missing message
- Volkswagen group code · Engine
- How the car detects it
- The engine computer expected a message from another module over the CAN network and didn't get it. The code names no single part: it says something went wrong on the network. Check the other modules' codes first; a weak battery, a voltage drop at start-up or a module whose software needs an update are the usual reasons. If it was stored once and doesn't come back, it is often harmless.
- What you may notice
- Often no symptom
- Sometimes warnings for other systems at the same time
- Likely causes
- PossibleA fault in the module that should send the data (see its own codes)
- PossibleLow battery voltage or a voltage drop when starting
- RareModule software that needs an update
- RareCAN wiring or connector
- Sources
- static.nhtsa.gov › MC-10123730-9999.pdf · official document
- static.nhtsa.gov › MC-11009334-0001.pdf · official document
- static.nhtsa.gov › MC-10233278-0001.pdf · official document
Backed by an official manufacturer document.
From Obdaryn's Volkswagen group pack, exactly as the app shows it, with the public sources above. Guidance only; confirm with a workshop.