U04A8 code meaning
Invalid Data Received From Hybrid/EV Battery Interface Control Module H
Network system Generic code U04xx codes Check engine light
What U04A8 means
U04A8 is the invalid-data code for interface module H. In GM's 2016 hybrid table 16OBDG02, H is the last of eight boards that the battery systems module reaches through a daisy chain; a pack of that design needs no higher letter. GM explains that a break anywhere in such a chain cuts off every board behind it, so lost contact is reported for the first board that cannot be recovered. An invalid-data code is different: if only H's frames fail the checks while A to G pass, the cause is more likely local to H, its connector or its cell inputs. No manufacturer documents U04A8 publicly. U01A7 means H is silent, U0341 a software mismatch. The driver sees a hybrid warning and may lose power.
U04A8 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1.5 to 8 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U04A8
- Hybrid system warning, MIL on plug-in hybrids
- Reduced propulsion power
Common causes of U04A8
- PossibleInterface control module H internally faulty
- PossibleConnector or lead fault at the last board of the chain
- Less likelyFaulty cell input on board H producing impossible values
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 h
What each part of U04A8 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| A8 | The exact fault in that area. |
What to do next
- Note U04A8 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 U04A8
What does U04A8 mean?
U04A8 means "Invalid Data Received From Hybrid/EV Battery Interface Control Module H". U04A8 is the invalid-data code for interface module H. It is a generic code, so it means the same on every make.
Is it safe to drive with U04A8?
Drive gently and only to a workshop. With U04A8 the car can go into limp mode (reduced power) to protect itself.
Will U04A8 fail an emissions test?
Yes, it can. U04A8 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 U04A8 to fix?
Difficulty: workshop only. A typical repair takes 1.5 to 8 hours of work. This is a job for a workshop.
Will U04A8 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.