U02A9 code meaning
Lost Communication With Charge Air Cooler Coolant Pump A
Network system Generic code U02xx codes Check engine light
What U02A9 means
Water-cooled charge air coolers need an electric pump in the low-temperature circuit, normally run by the engine controller as a LIN node. U02A9 means the pump has stopped answering. GM's 2025 tables (25OBDG04B) declare it after 2.5 s without a response while the pump is enabled and the supply is 11 to 18 V, and rate it Type A. GM bulletin 23-NA-102 for 2022 to 2025 Silverado, Sierra, Tahoe, Suburban, Yukon and Escalade with the 3.0 L diesel traces it to water entering the M10 pump connector, with or without LIN code U1345. FCA's Ram 1500 case shows pushed-out terminals at connector D2476A; on 2019 Jeep Renegades without grille shutters, an exposed inline connector corrodes. Mercedes reflashes the PTCU on the GLC. CARB requires charge air cooling to be monitored. Expect a MIL and less boost.
U02A9 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of U02A9
- MIL on
- Reduced boost or hesitation at high load
- Coolant warning or fan running at full speed on some models
Common causes of U02A9
- Most likelyWater or corrosion in the pump connector or an open inline connector
- PossibleTerminals pushed out of the pump connector
- PossibleSoftware of the LIN master controller needs an update
- Less likelyCharge air cooler pump electronics failed
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Cac coolant pump aVehicle bus wiring
What each part of U02A9 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| A9 | The exact fault in that area. |
What to do next
- Note U02A9 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U02A9
What does U02A9 mean?
U02A9 means "Lost Communication With Charge Air Cooler Coolant Pump A". Water-cooled charge air coolers need an electric pump in the low-temperature circuit, normally run by the engine controller as a LIN node. It is a generic code, so it means the same on every make.
Is it safe to drive with U02A9?
Drive gently and only to a workshop. With U02A9 the car can go into limp mode (reduced power) to protect itself.
Will U02A9 fail an emissions test?
Yes, it can. U02A9 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U02A9 to fix?
Difficulty: medium. A typical repair takes 0.3 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will U02A9 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.