U01BC code meaning
Lost Communication With Charge Air Cooler Coolant Pump B
Network system Generic code U01xx codes Check engine light
What U01BC means
Engines with a water-cooled charge air cooler run a separate low-temperature coolant loop with an electric pump, usually a LIN slave of the engine controller. Rheinmetall's pumps of this kind are driven via PWM or LIN, and Bosch's PCE pump has a built-in diagnostic function reported to a higher-level unit. U01BC applies where a second pump, B, serves this loop. No manufacturer documents the code publicly. For pump A, GM's 2025 tables (25OBDG04B) declare lost LIN contact after 2.5 s without a pump response while the pump is enabled, Type A, one trip, a sign of how strictly such losses are treated. CARB 1968.2 requires charge air undercooling to be detected, which a silent pump would hide. Expect a MIL and reduced boost or power when hot; U02A9 is pump A.
U01BC at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U01BC
- MIL on
- Reduced power or boost, especially in hot weather
Common causes of U01BC
- Most likelyWater or corrosion in the pump connector at the front of the engine bay
- PossiblePump supply fuse or relay open
- PossibleElectric coolant pump B electronics or motor faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Cac coolant pump bLin bus
What each part of U01BC means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| BC | The exact fault in that area. |
What to do next
- Note U01BC and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U01BC
What does U01BC mean?
U01BC means "Lost Communication With Charge Air Cooler Coolant Pump B". Engines with a water-cooled charge air cooler run a separate low-temperature coolant loop with an electric pump, usually a LIN slave of the engine controller. It is a generic code, so it means the same on every make.
Is it safe to drive with U01BC?
Drive gently and only to a workshop. With U01BC the car can go into limp mode (reduced power) to protect itself.
Will U01BC fail an emissions test?
Yes, it can. U01BC is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U01BC to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will U01BC clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.