U01A8 code meaning
Lost Communication With Hybrid/EV Battery Interface Control Module I
Network system Generic code U01xx codes Check engine light
What U01A8 means
U01A8 is the code for battery interface control module I and is only needed on packs with more than eight monitoring boards. GM's 2018 hybrid table contains it solely inside the fault bundle BICM Loss of Comm (U01A0-U01AC), adding that GM shares software across programs and only codes valid for the vehicle at hand apply; there is no monitor entry of its own, so neither threshold nor MIL type is published for I. Packs of that size exist: according to Wikipedia, the Ultium battery of the Hummer EV holds 24 modules, but which systems really use U01A8 remains undocumented. When it appears, the battery controller has lost the ninth board of its chain while the eight before it still answer. CARB requires separate codes per replaceable unit.
U01A8 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 8 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U01A8
- Battery or hybrid warning, power limited
- Charging blocked
Common causes of U01A8
- Most likelyChain connection between module H and module I interrupted
- PossibleBattery interface control module I defective
- Less likelyBattery controller configured for more boards than fitted
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 iCommunication bus
What each part of U01A8 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 U01A8 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 U01A8
What does U01A8 mean?
U01A8 means "Lost Communication With Hybrid/EV Battery Interface Control Module I". U01A8 is the code for battery interface control module I and is only needed on packs with more than eight monitoring boards. It is a generic code, so it means the same on every make.
Is it safe to drive with U01A8?
Drive gently and only to a workshop. With U01A8 the car can go into limp mode (reduced power) to protect itself.
Will U01A8 fail an emissions test?
Yes, it can. U01A8 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 U01A8 to fix?
Difficulty: workshop only. A typical repair takes 1 to 8 hours of work. This is a job for a workshop.
Will U01A8 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.