P2CB1: Charge Air Cooler Coolant Pump B Overspeed/Air In System

What it means

Charge air cooler coolant pump B reports a overspeed/air in system 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

Pump B circulates coolant through the charge air cooler loop, and its monitored speed can indicate whether coolant is moving as expected. This overspeed/air-in-system code sets when the pump reports unusually high speed associated with an air pocket or low coolant, which can leave the loop poorly filled and cooling ineffective.

Common causes

Most likely first.

1. Air pocket in coolant loop
2. Coolant level low

Symptoms

• Check-engine light
• Reduced engine power
• Possible charge-air temperature warning

How to diagnose it

1. Capture freeze-frame data and check pump B speed and charge-air temperature data, if available, for signs of erratic circulation.
2. With the engine cool, check the charge air cooler loop coolant level using the manufacturer's procedure and inspect for leaks.
3. Inspect pump B and the loop hoses for loose connections, visible air entry, kinks, or damage.
4. Check whether pump B runs noisily or erratically during a supported scan-tool output test while observing the loop as directed by service information.
5. If the level and connections are correct, bleed the loop using the manufacturer's procedure and recheck pump speed and circulation.

Common fixes

• Refill the charge air cooler loop with the specified coolant if its level is low.
• Repair a leak or loose connection that allows coolant loss or air entry.
• Bleed trapped air from the loop using the manufacturer's procedure.
• Replace pump B if its speed remains abnormal after the loop is correctly filled and bled.

Can I keep driving?

Avoid heavy loads and sustained acceleration until coolant level and circulation are restored, since charge-air temperature can rise and engine power may be limited. Stop if a temperature warning appears or power falls sharply.