U01A1 code meaning
Lost Communication With Hybrid/EV Battery Interface Control Module B
Network system Generic code U01xx codes Check engine light
What U01A1 means
U01A1 refers to battery interface control module B. In GM's eAssist mild hybrids it is the second and final board: bulletin PIT5513D lists two high-voltage battery interface control modules, K112A and K112B, for Silverado and Sierra trucks of 2016 to 2018 and the 2018 LaCrosse, and the GM tables 16OBDG07B and 19OBDG03B accordingly contain only U01A0 and U01A1. Their rating is milder than in the plug-in hybrids: Type B, so the MIL waits for a second failing trip; the 2016 table asks for more than 9.1 V and 4.5 s. If B is logged alone, the fault lies at B or at the link from A to B; both letters together point rather to a shared feed or the master side. GM placed these powerpacks and both boards under parts restriction via its technical assistance center.
U01A1 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 6 hours
- Clears after repairAfter a drive cycle
Symptoms of U01A1
- MIL only after two consecutive failing trips (GM Type B)
- Start-stop and electric assist unavailable
- Hybrid system warning message
Common causes of U01A1
- Most likelyChain connection between module A and module B interrupted or corroded
- PossibleBattery interface control module B (GM K112B) defective
- Less likelyCommon low-voltage feed of the powerpack interrupted (then usually A as well)
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 bCommunication bus
What each part of U01A1 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| A1 | The exact fault in that area. |
What to do next
- Note U01A1 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 U01A1
What does U01A1 mean?
U01A1 means "Lost Communication With Hybrid/EV Battery Interface Control Module B". U01A1 refers to battery interface control module B. It is a generic code, so it means the same on every make.
Is it safe to drive with U01A1?
Drive gently and only to a workshop. With U01A1 the car can go into limp mode (reduced power) to protect itself.
Will U01A1 fail an emissions test?
Yes, it can. U01A1 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 U01A1 to fix?
Difficulty: workshop only. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will U01A1 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.