U0640Lost Communication With EVAP Fuel Vapor Temperature Sensor Circuit
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- Many fuel tank pressure senders also measure the temperature of the vapor in the tank, and when such a sender reports digitally, typically over SENT, both values share one data stream. U0640 is stored when the engine controller no longer receives valid temperature data from this sensor. Despite the word circuit in the title, the fault concerns the digital link; an analog vapor temperature sensor reports wiring faults as P2024 to P2028. Audi documents U0640 together with U0641 for 2021–2023 A4 and A5 models with the 2.0 TFSI EA888: electrical interference on the vent system signal sets both codes sporadically, the cure is swapping two wires of a twisted bundle in the harness, and a new sender does not help. The MIL comes on, while the car drives normally.
- What you may notice
- Check engine light on
- Often stored together with U0641
- Evaporative system monitor does not complete
- Likely causes
- LikelyInterference or chafing on the shared signal line of the tank pressure/temperature sender
- PossibleLoose or corroded connector at the tank sender
- RareElectronics of the sender failed (only if the code is stored permanently)
- RareEngine controller software or input fault
- 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 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.