U05AA code meaning
Invalid Data Received From Charge Air Cooler Coolant Pump
Network system Generic code U05xx codes Check engine light
What U05AA means
Engines with a water-cooled charge air cooler use an electric pump, often a LIN slave of the engine controller, to move coolant through the low-temperature circuit. CARB requires the charge air cooling to be checked for performance and its electronic parts to be monitored. U05AA is set when the pump reports speed, current or fault bits that do not make sense. Public maker documentation exists for the partner U02A9: GM's 2025 tables declare lost LIN contact after 2.5 s without a pump response, Type A; Ram 1500 owners see a check engine light with U02A9 and P023B from pushed-out terminals at the pump connector; Mercedes links U02A900 on GLC and GLE to the PTCU software or LIN wiring. None documents U05AA itself. Expect reduced boost if intake air runs hot.
U05AA at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.3 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of U05AA
- Check engine light on
- Reduced engine power in hot conditions
- Coolant warning or radiator fan running at full speed
Common causes of U05AA
- Most likelyPushed-out or corroded terminals at the pump connector
- PossibleFault elsewhere on the shared LIN bus or in the master module software
- PossiblePump electronics or motor faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Cac coolant pump
What each part of U05AA means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| AA | The exact fault in that area. |
What to do next
- Note U05AA 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 U05AA
What does U05AA mean?
U05AA means "Invalid Data Received From Charge Air Cooler Coolant Pump". Engines with a water-cooled charge air cooler use an electric pump, often a LIN slave of the engine controller, to move coolant through the low-temperature circuit. It is a generic code, so it means the same on every make.
Is it safe to drive with U05AA?
Drive gently and only to a workshop. With U05AA the car can go into limp mode (reduced power) to protect itself.
Will U05AA fail an emissions test?
Yes, it can. U05AA 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 U05AA to fix?
Difficulty: medium. A typical repair takes 0.3 to 2 hours of work. This is a job for a workshop.
Will U05AA 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.