U0140

Universal

Lost Communication With Body Control Module

Definition source: General OBD-II reference catalog
Definition verification: Not independently verified for display.
Time: Varies by diagnosis and vehicle | Diagnostic difficulty: Medium
Medium Severity

One or more vehicle modules have detected that they cannot communicate with the Body Control Module (BCM) over the vehicle network. The BCM coordinates various body-related functions, but which functions it controls varies by vehicle. A communication loss may affect those functions, or the code may be stored without obvious symptoms. It does not by itself prove the BCM needs replacement.

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⚠️ Before You Begin (Safety First)

Check that essential exterior lights, turn signals, wipers, and other safety-related functions work before driving. Do not drive if a fault leaves required lights or controls inoperative, or if the vehicle behaves unpredictably. Seek qualified help if the warning is accompanied by starting or drivability problems.

Common Symptoms

  • There may be no noticeable symptoms if the communication loss is intermittent or does not affect a function the driver uses.
  • Body-related features such as interior or exterior lighting, locks, windows, or wipers may malfunction if they depend on the BCM.
  • Warning messages or indicator lights may appear when other modules cannot receive information from the BCM.
  • Starting or other vehicle functions may be affected on some vehicles if they rely on BCM communication; this varies by design.

Common Causes

  • A weak or unstable vehicle battery or charging supply can interrupt module communication.
  • A blown fuse, poor power connection, or poor ground can prevent the BCM from operating or communicating.
  • Damaged, loose, corroded, or moisture-affected wiring or connectors can disrupt the BCM's network connection.
  • A fault elsewhere on the vehicle communication network can prevent messages from reaching the BCM or other modules.
  • The BCM may have an internal fault, but this should be considered only after its power, grounds, connections, and network circuits are checked.

Diagnostic Steps

  1. Note any warning messages and which body-related functions are not working; this helps show whether the communication problem has practical effects.
  2. Check the battery terminals for looseness or visible corrosion and have the battery and charging system checked if starting or electrical problems are present.
  3. Using the owner's manual, identify and visually check fuses related to the BCM or affected functions. Replace a fuse only with the specified type and rating; if it blows again, stop and seek diagnosis.
  4. With the vehicle safely parked, look for accessible signs of damaged wiring, loose connectors, or moisture near areas that may have been disturbed during recent work. Do not unplug modules or probe network wiring.
  5. If an appropriate scan tool is available, record codes from all modules before clearing anything. A qualified technician may need to determine which modules can and cannot communicate.

When to Call a Professional

Use a scan tool capable of communicating with all vehicle modules. Compare which modules report communication faults and check related codes and network status. Follow vehicle-specific service information to test BCM power and grounds, fuses, connectors, wiring, and network circuits before considering module replacement. Programming or configuration may be required if a module is replaced.

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Commonly Asked Questions

Does U0140 mean the Body Control Module has failed?

No. The code reports a loss of communication, which can result from a power, ground, wiring, connector, or network problem as well as a possible BCM fault. Testing is needed before replacing parts.

Can I keep driving with U0140?

It depends on which functions are affected. Check essential lights and controls before driving, and do not drive if required safety functions are inoperative or the vehicle behaves unpredictably.

Why are there no obvious symptoms?

The communication interruption may be intermittent, or it may affect information that does not produce a noticeable change in normal driving.

What helps distinguish a BCM fault from a network problem?

A scan of all modules, along with vehicle-specific checks of BCM power, grounds, connectors, wiring, and network circuits, helps identify whether the problem is local to the BCM or elsewhere. The exact test procedure depends on the vehicle.

Browse Available Code Guides

Previous and next available guides in database record order, across makes. Adjacent entries may share a code number and do not necessarily describe related faults.