U0642Lost Communication With EVAP System Pressure Sensor/Switch Circuit B
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- A second EVAP pressure sensor, B, appears where one reading is not enough, for instance when tank and canister are separated by an isolation valve and each side needs its own value, as in sealed tanks of plug-in hybrids that see higher pressures. Which location is called B is up to the manufacturer. U0642 is the lost-communication code for this sensor when it reports digitally; its analog counterpart logs P24D5 to P24D9. No manufacturer documents U0642 publicly. Because CARB 1968.2 (e)(15.2.1)(B)(i) demands a separate code for a digital input that stops talking, the code exists independently of U0641. While B is silent, the controller cannot compare both sides or check the isolation valve, so the leak test is suspended and a MIL is to be expected.
- What you may notice
- MIL on
- EVAP monitor incomplete
- On sealed tanks possibly a delayed fuel door release
- Likely causes
- LikelySignal, supply or ground line to sensor B open or chafed
- PossibleCorroded or unplugged connector at sensor B
- PossibleSensor B electronics failed
- RareReceiving controller input or software 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 – €450
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.