U04AA code meaning
Invalid Data Received From Hybrid/EV Battery Interface Control Module J
Network system Generic code U04xx codes Check engine light
What U04AA means
U04AA flags invalid data from interface module J, the tenth slot. From here on the series only matters for packs with ten or more monitored sections; a nine-module ID.4 battery or an eight-board GM pack like the one in table 16OBDG02 has no J at all. GM's Ultium family, by contrast, assembles packs from anywhere between six and 24 modules of one design, per Wikipedia, and the larger ones clearly exceed ten. No manufacturer publishes U04AA or a threshold for it, and none of the indexed service bulletins mentions it. Likely triggers are the same as for the lower letters: a disturbed isolated link, a damaged connector or a faulty board. U01A9 means J is silent, U0343 incompatible software.
U04AA at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1.5 to 10 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U04AA
- Battery or EV system warning
- Power or charging rate reduced
Common causes of U04AA
- PossibleDisturbed isolated data link inside the pack
- PossibleDamaged connector at module J
- PossibleInterface control module J faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hv battery interface module j
What each part of U04AA 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 U04AA 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 U04AA
What does U04AA mean?
U04AA means "Invalid Data Received From Hybrid/EV Battery Interface Control Module J". U04AA flags invalid data from interface module J, the tenth slot. It is a generic code, so it means the same on every make.
Is it safe to drive with U04AA?
Drive gently and only to a workshop. With U04AA the car can go into limp mode (reduced power) to protect itself.
Will U04AA fail an emissions test?
Yes, it can. U04AA 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 U04AA to fix?
Difficulty: workshop only. A typical repair takes 1.5 to 10 hours of work. This is a job for a workshop.
Will U04AA clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.