U01BC: Lost Communication With Charge Air Cooler Coolant Pump B

What it means

Communication with Charge Air Cooler Coolant Pump B was not received as expected. This code does not by itself establish the effect on engine performance or other systems.

At a glance

• Usually lights the warning light of the system that lost communication
• Affects emissions; the car can fail an emissions test

How it works

Charge Air Cooler Coolant Pump B circulates coolant through the charge-air cooling system, and its control electronics report status over the vehicle network. This code sets when the expected messages from pump B are not received; it does not alone confirm whether the pump has stopped or how much engine performance is affected.

Common causes

Most likely first.

1. Module unpowered
2. Gateway module routing CAN messages incorrectly
3. CAN 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

How to diagnose it

1. Record freeze-frame data and all module codes, and note whether the fault appears with engine-temperature, boost, or emissions warnings.
2. Use a compatible scan tool to check whether Charge Air Cooler Coolant Pump B responds and whether pump status or commanded operation is reported.
3. Inspect pump B’s power, ground, connector, and nearby wiring for looseness, corrosion, heat damage, or coolant contamination.
4. Check the network wiring and connectors on the pump’s communication branch for opens, shorts, or poor contact.
5. If its supply and network wiring are sound, test gateway routing and CAN termination to the manufacturer’s specification.

Common fixes

• Clean and secure pump B’s low-voltage power, ground, or connector connection.
• Repair damaged or coolant-contaminated wiring and connector terminals at pump B.
• Correct a confirmed gateway routing fault.
• Repair or replace a CAN terminating resistor if it fails specification checks.

Can I keep driving?

Avoid heavy acceleration, towing, or prolonged high-load driving until the pump communication fault is resolved, especially if temperature or boost warnings appear. Continued operation with inadequate charge-air cooling can reduce performance and may cause further engine or emissions-system problems.