U02A9: Lost Communication With Charge Air Cooler Coolant Pump A

What it means

The vehicle bus reports loss of communication with charge air cooler (intercooler) coolant pump A. Intake-charge cooling on indirect intercooler systems cannot be controlled, raising knock risk and reducing power.

At a glance

• Usually lights the warning light of the system that lost communication
• The engine or gearbox may go into limp mode

How it works

Charge air cooler coolant pump A circulates coolant through the indirect intercooler circuit to remove heat from the engine's intake air. U02A9 sets when the network stops receiving messages from pump A, so the controller cannot command or verify that cooling circuit and may limit engine output.

Common causes

Most likely first.

1. Bus wiring open or shorted
2. Module without power or ground
3. Module failed

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. Scan all modules and save freeze-frame data, including intake-air temperature and any reduced-power or network codes.
2. Review live data for charge-air coolant temperature and pump A status to see whether the pump is missing from the network or reporting an operating fault.
3. With the vehicle cool, inspect pump A's connector and harness for loose connections, corrosion, chafing, or coolant contamination.
4. Check pump A's power and ground using the manufacturer's wiring information and test conditions.
5. Test the pump's network wiring for opens, shorts, or poor connections using the manufacturer's procedure.
6. If supplies and network wiring pass, verify pump A has failed before replacement, then confirm coolant level and circuit condition as specified by the manufacturer.

Common fixes

• Reconnect or repair a loose or corroded pump A connector.
• Repair damaged wiring at charge air cooler coolant pump A.
• Restore the pump's power or ground connection.
• Repair an open or short in pump A's network circuit.
• Replace charge air cooler coolant pump A if its supplies and network wiring pass testing.

Can I keep driving?

Avoid hard acceleration, towing, or sustained high boost because loss of charge-air cooling can raise intake temperatures and increase knock risk. If reduced power or an overheating warning appears, stop driving when safe and have the fault addressed promptly.