U01AA code meaning
Lost Communication With Hybrid/EV Battery Interface Control Module K
Network system Generic code U01xx codes Check engine light
What U01AA means
U01AA covers battery interface control module K, the eleventh board, so only large packs can set it at all. Not every design uses wires for this link: GM's Ultium platform monitors its cells by radio, a system developed with Analog Devices, which according to Wikipedia needs about 90 % less wiring. With such a layout a lost module is a radio node the controller no longer hears; checks then move from harness and plugs to the node's supply, interference and the correct registration of any replacement board. No manufacturer publicly ties U01AA to a vehicle; GM includes it only in the fault bundle of its 2018 hybrid table, which lists module codes up to M, without a monitor entry or MIL type of its own.
U01AA at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 10 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U01AA
- Battery warning, reduced range and power
- DC fast charging limited or refused
Common causes of U01AA
- Most likelyWired link to K interrupted or, in wireless systems, radio link lost
- PossibleReplacement board K not registered with the battery controller
- Less likelyBattery interface control module K defective
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 kCommunication bus
What each part of U01AA 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 U01AA 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 U01AA
What does U01AA mean?
U01AA means "Lost Communication With Hybrid/EV Battery Interface Control Module K". U01AA covers battery interface control module K, the eleventh board, so only large packs can set it at all. It is a generic code, so it means the same on every make.
Is it safe to drive with U01AA?
Drive gently and only to a workshop. With U01AA the car can go into limp mode (reduced power) to protect itself.
Will U01AA fail an emissions test?
Yes, it can. U01AA 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 U01AA to fix?
Difficulty: workshop only. A typical repair takes 1 to 10 hours of work. This is a job for a workshop.
Will U01AA clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.