U01B0 code meaning
Lost Communication With Battery Monitor Module
Network system Generic code U01xx codes Check engine light
What U01B0 means
U01B0 says the 12 V battery monitor module, a small sensor on the negative battery post that reports voltage, current, temperature and state of charge, has stopped replying. GM polls it over LIN: its 2018 engine tables (18OBDG03A) flag the code once frame 18_C02 has been absent for 1.25 s, the 2025 body controller tables (25OBDG04A) after 12.6 s; both rate it Type B, two trips. GM bulletins 15-NA-087 and 22-NA-214 list it with a disabled stop/start system and a lit MIL, have the battery and LIN wiring checked first and the sensor swapped last; afterwards it must relearn, which a parasitic drain above about 250 mA blocks. Volkswagen lists U01B000 with MIL in the engine controller of the 2024 Atlas. U04B1 is the invalid-data partner.
U01B0 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of U01B0
- Stop/start system disabled, message in the driver display
- MIL on
- Battery state of charge shown wrongly or battery saver functions inactive
Common causes of U01B0
- Most likelyLoose, corroded or damaged LIN connector or wire at the battery sensor
- PossibleWeak or deeply discharged 12 V battery
- PossibleBattery monitor sensor faulty (GM replaces it after the checks)
- Less likelyParasitic drain preventing the sensor relearn
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Battery monitor moduleLin bus
What each part of U01B0 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| B0 | The exact fault in that area. |
What to do next
- Note U01B0 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 U01B0
What does U01B0 mean?
U01B0 means "Lost Communication With Battery Monitor Module". U01B0 says the 12 V battery monitor module, a small sensor on the negative battery post that reports voltage, current, temperature and state of charge, has stopped replying. It is a generic code, so it means the same on every make.
Is it safe to drive with U01B0?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will U01B0 fail an emissions test?
Yes, it can. U01B0 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 U01B0 to fix?
Difficulty: medium. A typical repair takes 0.3 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will U01B0 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.