OBD-II code · Network
U01BC Lost Communication With Charge Air Cooler Coolant Pump B
ECU lost communication with the second CAC coolant pump module. A communication loss with this module breaks any function relying on its data — diagnostic tools may show 'no response' and dependent modules can fall into limp mode.
Is it safe to drive with U01BC?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyModule unpowered
- Less likelyGateway module routing CAN messages incorrectly
- Less likelyCAN terminating resistor (120 Ω) drifted out of spec
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
- Often, with basic tools
- Typical labour
- 0.5–4 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Cac Coolant Pump B, Can Bus
Related codes
- U02A9Lost Communication With Charge Air Cooler Coolant Pump A
- U01B9Lost Communication With Switch Input Module C
- U01BALost Communication With Park Lock/Pawl Control Module
- U01BBLost Communication With Battery Charger Control Module B
- U01BDLost Communication With DC/DC Converter Control Module C
- U01BELost Communication with Drive Motor A Clutch Actuator
- U01BFLost Communication with Battery Management Control Module
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.