What it means
Charge air cooler coolant pump B reports a control circuit low condition. CAC coolant loop circulation is impaired.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Coolant pump B moves coolant through the charge air cooler loop to reduce the temperature of compressed intake air. This circuit-low code sets when the ECM sees a control-circuit signal below its expected range, which can point to a short to ground, an internally shorted pump motor, or poor connector contact.
Common causes
Most likely first.
- Control wire shorted to ground
- Internal short in pump motor
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light
- Reduced engine power or acceleration
- Charge-air temperature warning, if equipped
How to diagnose it
- Save freeze-frame data and check for related pump B or charge-air temperature codes before clearing anything.
- With the engine off, inspect pump B's connector for corrosion, loose terminals, or heat or water damage.
- Inspect the pump B control wire for rubbing or pinching that could short it to ground.
- Test the control circuit for a short to ground and check pump B's motor electrically using the vehicle wiring information.
- Compare circuit and motor test results with the manufacturer's specification to separate a harness fault from an internally shorted pump.
Common fixes
- Clean or repair corroded pump B connector terminals and restore firm contact.
- Repair the control wire where it is shorted to ground.
- Replace pump B if its motor is internally shorted or outside the manufacturer's specification.
- Repair a confirmed control circuit connection fault.
Can I keep driving?
Limit hard acceleration, high-speed driving, and towing because poor charge-air cooling can lead to reduced engine power. Stop if a charge-air temperature warning appears or the engine begins losing substantial power.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.