A weak or failing battery or poor battery terminal connections causing low voltage on the network; Corroded, loose or damaged BCM connector pins or terminals; A blown fuse or poor ground serving the BCM; Wiring damage in the CAN bus or BCM power/ground circuits, often from rodent damage or chafing; A failed BCM, though this is less common than wiring and power faults; Another module on the bus holding the network down and disrupting communication; Aftermarket accessories or poor previous repairs tapping into body wiring

DTC codes / U01xx · Lost communication with a control module / U0155

U0155Lost Communication With Body Control Module

Q: What does code U0155 mean?

Lost Communication With Body Control Module. U0155 means the modules on the vehicle's Controller Area Network (CAN) bus have stopped receiving messages from the Body Control Module (BCM), the module that runs locks, lights, wipers and other body functions. The computer that set the code detected a loss of the BCM's periodic heartbeat or a timeout in expected BCM messages, not necessarily that the BCM itself has failed.

U0155 means the modules on the vehicle's Controller Area Network (CAN) bus have stopped receiving messages from the Body Control Module (BCM), the module that runs locks, lights, wipers and other body functions. The computer that set the code detected a loss of the BCM's periodic heartbeat or a timeout in expected BCM messages, not necessarily that the BCM itself has failed.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaLost communication with a control module

Symptoms you may notice

Often no symptoms besides the warning light, because the BCM may still be working while only its network messages are disrupted
Multiple unrelated body functions acting up at once, such as interior lights, power locks, wipers or turn signals
The engine may still start and run normally, but other modules may log communication faults
Intermittent operation of body electrical features that come and go with vibration or temperature
A no-start condition on vehicles where the BCM participates in the immobilizer handshake
Other warning lights or messages on the dash from modules that lost their BCM data

Common causes, most likely first

A weak or failing battery or poor battery terminal connections causing low voltage on the network
Corroded, loose or damaged BCM connector pins or terminals
A blown fuse or poor ground serving the BCM
Wiring damage in the CAN bus or BCM power/ground circuits, often from rodent damage or chafing
A failed BCM, though this is less common than wiring and power faults
Another module on the bus holding the network down and disrupting communication
Aftermarket accessories or poor previous repairs tapping into body wiring

How to diagnose and fix it

Scan all modules for communication codes and record which modules can and cannot talk to the BCM
Test battery voltage and load, and clean and tighten battery terminals and grounds
Check the BCM fuses and confirm power and ground at the BCM connector with a multimeter
Inspect BCM connectors and harnesses for corrosion, pushed pins, chafing or rodent damage
Measure CAN bus resistance and voltage to confirm the bus is healthy and not shorted
If the bus and power checks pass, substitute a known-good BCM or perform module programming as required
Clear codes and road test, then recheck for returning communication faults

What U0155 does not always mean

A U0155 does not automatically condemn the BCM, because low battery voltage or a bad ground can silence it on the network while the module itself is fine.
Many vehicles set U0155 as a secondary code after a dead battery or jump start, and the code clears once voltage is restored and the network reinitializes.
A single failed module on the CAN bus can disrupt communication for several modules, so the BCM may be the victim rather than the cause.
Aftermarket alarms, remote starters or audio installs that tap body wiring are a frequent hidden cause of intermittent U0155 faults.
On some platforms the BCM is part of the immobilizer path, so a no-start with U0155 should prompt a check of the BCM power and ground before replacing it.

Can I keep driving with U0155?

The vehicle may remain drivable because the engine control module usually runs independently, but body electrical functions and immobilizer operation can be affected. Avoid long trips and have the fault diagnosed soon, and do not continue driving if the engine will not start or safety systems are disabled.

Tools that help

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