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DTC codes / U01xx · Lost communication with a control module / U019B

U019BLost Communication With Battery Charger Control Module A

U019B means the vehicle's main computers have lost contact with the Battery Charger Control Module A, a dedicated controller for high-voltage battery charging on electrified vehicles. The computer that set the code was expecting regular status messages from that module over the communication network and stopped receiving them for a set period.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaLost communication with a control module

Symptoms you may notice

  • Illuminated check engine light or service vehicle soon message on the dashboard
  • A charging system warning or high-voltage battery fault message displayed
  • The vehicle may refuse to start or enter ready mode, or may start but not accept a charge
  • Reduced power or limp-home mode if the battery state of charge cannot be managed
  • Often no symptoms besides the warning light when communication is intermittent
  • Charging schedule or remote charge features may stop working

Common causes, most likely first

  1. A blown fuse or tripped circuit breaker feeding the Battery Charger Control Module A
  2. Damaged, corroded or loose wiring or connector pins at the charger control module
  3. A failed Battery Charger Control Module A internal communication fault
  4. CAN (Controller Area Network) bus wiring damage or a shorted network segment
  5. Low 12-volt battery voltage or poor grounds causing modules to drop offline
  6. A software or configuration mismatch after module replacement or battery service
  7. Water intrusion or heat damage affecting the charger control module or its harness

How to diagnose and fix it

  1. Verify the 12-volt battery is fully charged and load-test it, then clear the code and recheck
  2. Check all fuses and circuit breakers that supply the Battery Charger Control Module A and its network gateway
  3. Inspect the charger control module connectors and harness for corrosion, pushed pins, chafing or water intrusion
  4. Measure CAN bus voltages and resistance at the diagnostic connector to confirm the network is healthy
  5. Use a scan tool to check whether other modules can communicate with the charger control module and perform a network integrity test
  6. If communication is absent at the module, check its power, ground and wake-up signals before condemning it
  7. After any repair, clear codes and perform a full drive cycle including a charging session to confirm the code does not return

Charger module communication faults that fool technicians

  • A weak or failing 12-volt battery is a common hidden cause because modules shut down or reset when supply voltage sags during cranking or charging.
  • The code can be set by a network gateway or central computer that simply cannot hear the charger module, so the fault may live in the gateway or its wiring rather than the charger itself.
  • Intermittent U019B often appears after heavy rain or a car wash when water reaches a connector, then clears once the harness dries out.
  • Replacing the charger control module without checking power, ground and network wake signals frequently leaves the same code stored because the original fault was in the harness.
  • Some vehicles set this code during a failed over-the-air update or after a module is disconnected with the ignition on, and it may clear after a proper sleep cycle.

Can I keep driving with U019B?

If the vehicle still starts and drives normally, you can drive it to a workshop, but avoid long trips and do not rely on charging until the fault is diagnosed. If the vehicle will not start, will not charge, or shows a high-voltage battery warning, stop driving and have it towed.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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