U01B0Lost Communication With Battery Monitor Module
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Stop/start system disabled, message in the driver display
- MIL on
- Battery state of charge shown wrongly or battery saver functions inactive
- Likely causes
- 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)
- RareParasitic drain preventing the sensor relearn
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €0 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.