OBD-II code · Network
U0633 Lost Communication With Fan 2
The vehicle bus reports loss of communication with smart cooling fan 2 (PWM brushless fan with own controller). Fan speed cannot be commanded; cooling falls back to default operation.
Is it safe to drive with U0633?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
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
- 0.5–3 h
- Emissions test
- Usually unaffected
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Cooling Fan 2, Vehicle Bus Wiring
Related codes
- U0630Lost Communication With Engine Coolant Temperature Sensor 4
- U0631Lost Communication With Engine Coolant Temperature Sensor 5
- U0632Lost Communication With Fan 1
- U0634Lost Communication With Hybrid/EV Battery Pack Coolant Temperature Sensor A
- U0635Lost Communication With Hybrid/EV Battery Pack Coolant Temperature Sensor B
- U0636Lost Communication With Hybrid/EV Battery Pack Coolant Control Valve A
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.