U04A3 code meaning
Invalid Data Received From Hybrid/EV Battery Interface Control Module C
Network system Generic code U04xx codes Check engine light
What U04A3 means
U04A3 concerns interface module C. Such boards do more than measure: they also switch the balancing resistors that bleed charge from individual cells. CARB 1968.2 section (e)(15.2.3) requires hybrid OBD to confirm that cell balancing still holds the cell voltages where intended, and GM checks this per board in 16OBDG02 by closing the odd and even balancing gates in turn and comparing readings, for module C under P1E9E. When the battery controller cannot trust what module C sends, it can neither balance nor judge those cells, so it usually limits power. No manufacturer publishes U04A3 itself. U01A2 marks a silent module C, U033C incompatible software; module D's data fault is filed as U02A0, because U04A4 belongs to the particulate sensor.
U04A3 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 U04A3
- Hybrid or EV warning, MIL on plug-in hybrids
- Power limited, state of charge shown inaccurately
Common causes of U04A3
- PossibleInterface control module C faulty (measurement or balancing stage)
- PossibleDamaged cell sense lead or connector at module C
- PossibleInterference or contact fault on the pack-internal data link
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 c
What each part of U04A3 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| A3 | The exact fault in that area. |
What to do next
- Note U04A3 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 U04A3
What does U04A3 mean?
U04A3 means "Invalid Data Received From Hybrid/EV Battery Interface Control Module C". U04A3 concerns interface module C. It is a generic code, so it means the same on every make.
Is it safe to drive with U04A3?
Drive gently and only to a workshop. With U04A3 the car can go into limp mode (reduced power) to protect itself.
Will U04A3 fail an emissions test?
Yes, it can. U04A3 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 U04A3 to fix?
Difficulty: workshop only. A typical repair takes 1.5 to 8 hours of work. This is a job for a workshop.
Will U04A3 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.