OBD-II code · Network
U0642 Lost Communication With EVAP System Pressure Sensor/Switch Circuit B
The vehicle bus reports loss of communication with smart EVAP system pressure sensor / switch B. Tank-pressure-based leak detection cannot run on this channel.
Is it safe to drive with U0642?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyBus wiring open or shorted
- PossibleModule without power or ground
- PossibleModule failed
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.5–2 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Evap Pressure Sensor B, Vehicle Bus Wiring
Related codes
- U0641Lost Communication With EVAP System Pressure Sensor/Switch Circuit A
- U063FLost Communication With Engine Coolant Flow Control Valve Position Sensor
- U0640Lost Communication With EVAP Fuel Vapor Temperature Sensor Circuit
- U0643Lost Communication With Turbocharger/Supercharger A Temperature Sensor
- U0644Lost Communication With Wastegate Position Sensor A
- U0645Lost Communication With Active Air Dam Module
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.