U0641Lost Communication With EVAP System Pressure Sensor/Switch Circuit A
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- Pressure sensor A is the main input for the evaporative leak test that CARB 1968.2 (e)(4) requires: with the system sealed, the controller follows how pressure in tank and canister rises or falls. Newer designs often use a relative pressure sensor with SENT output; Melexis' MLX90821, for example, spans about −0.06 to 0.26 bar in its SENT version and can add a media temperature. U0641 means these digital messages are missing or unusable, which (e)(15.2.1)(B)(i) treats as its own fault; an analog sensor would log P0450 to P0454. Audi's 2.0 TFSI bulletin for 2021–2023 A4/A5 separates sporadic entries, caused by interference and fixed in the harness, from permanent ones that need normal diagnosis. The leak test stays blocked and the MIL is on.
- What you may notice
- MIL on
- EVAP leak monitor not ready, possible inspection failure
- No noticeable change in driving
- Likely causes
- LikelyElectrical interference or damage on the sensor signal line
- PossibleConnector at the tank or canister sensor loose, wet or corroded
- PossiblePressure sensor A itself no longer sends
- RareSensor supply or ground missing
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €40 – €450
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.