OBD-II code · Network
U0631 Lost Communication With Engine Coolant Temperature Sensor 5
The vehicle bus reports loss of communication with smart engine coolant temperature sensor 5. Thermal management loses one of its temperature inputs and may use a substitute value.
Is it safe to drive with U0631?
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
- Easy
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.5–1.5 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Ect Sensor 5, Vehicle Bus Wiring
Related codes
- U0630Lost Communication With Engine Coolant Temperature Sensor 4
- U062ELost Communication With A/C Refrigerant Expansion Valve Actuator
- U062FLost Communication With Coolant Pump C
- U0632Lost Communication With Fan 1
- U0633Lost Communication With Fan 2
- U0634Lost Communication With Hybrid/EV Battery Pack Coolant Temperature Sensor A
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.