U1121Data bus: missing message

• Volkswagen group code · Airbag (SRS)

How the car detects it

The airbag unit 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. While an airbag fault is stored, the affected airbag or pretensioner may not deploy in a crash. Have it repaired before relying on it. Never probe airbag connectors with a meter: that can fire the airbag.

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.