P2B84: Charge Air Cooler Coolant Pump A Underspeed

What it means

The charge air cooler coolant pump A runs below the calibrated minimum speed for the commanded duty. Mechanical resistance high or supply voltage low.

At a glance

• Usually lights the check-engine light
• The engine or gearbox may go into limp mode

How it works

Charge-air cooler coolant pump A circulates coolant to remove heat from compressed intake air. This code sets when pump A turns more slowly than the module commands, pointing to binding or inadequate electrical supply and potentially reduced cooling under load.

Common causes

Most likely first.

1. Mechanical load increased (binding)
2. Supply voltage low under load

Symptoms

• Check-engine light
• Reduced engine power under load
• Charge-air cooling performance may be reduced

How to diagnose it

1. Record freeze-frame data and compare pump A's commanded duty with its reported speed and charge-air temperatures.
2. With the system cool, check the charge-air cooler coolant level and inspect the pump and hoses for leaks, obstructions, or damage.
3. Inspect pump A's connector, wiring, fuse protection, and grounds for corrosion, looseness, or heat damage.
4. Measure voltage at pump A while it is commanded on and loaded, comparing the supply and ground drop with the manufacturer's specification.
5. If supply and wiring pass, check pump A for mechanical binding and compare its speed response with the manufacturer's specification.

Common fixes

• Repair a loose, corroded, or damaged electrical connection to pump A.
• Repair a restricted or damaged coolant hose and refill the loop as needed.
• Correct an inadequate power or ground supply to the pump.
• Replace pump A if it binds or remains below commanded speed with correct supply voltage.

Can I keep driving?

The fault can reduce charge-air cooling and trigger power limits under load; avoid towing and hard acceleration until repaired. Stop if the vehicle develops overheating warnings or coolant loss.