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Overview

U0140 Lost Communication With Body Control Module (BCM) diagnostic; possible causes BCM failure, wiring harness or CAN bus communication loss; symptoms and diagnostic guidance

Common Symptoms

Check engine or warning light illuminate
Body electrical functions (lights, door locks, windows) malfunction
Erratic interior/exterior lighting
Remote keyless entry failure
Blown fuses or inability to start in severe cases

Most Common Causes

Faulty Body Control Module (BCM) high

BCM fails to transmit/receive CAN messages correctly

Damaged or loose wiring and connectors in BCM circuit high

CAN bus lines, power or ground faults can interrupt communication

CAN bus communication failure medium

Shorts, opens, or network termination issues on CAN high/low

Low battery voltage or power supply issues medium

Voltage drop can cause module communication dropout

Diagnostic Steps

Scan vehicle modules with OBD‑II diagnostic scanner

Expected: Identify active U0140 and any accompanying U‑codes

Interpretation: Multiple network codes suggest CAN bus problem
Check battery voltage and BCM related fuses

Expected: Battery should read ~12.2‑12.8 V; fuses intact

Interpretation: Low voltage or blown fuse could cause communication loss
Inspect BCM connectors and wiring harness for corrosion, looseness or damage

Expected: Clean, secure connections and intact wires

Interpretation: Poor physical connection often underlies communication error
Use multimeter to test CAN high and CAN low continuity and check for shorts

Expected: Continuity without short to ground

Interpretation: CAN network fault indicates wiring issue
Attempt direct communication with BCM using advanced scan tool

Expected: Module responds to commands

Interpretation: Non‑responsive BCM suggests module failure

Repair Solutions

Repair or replace damaged wiring/connectors in BCM circuit medium

Estimated Cost: $50 - $300

Fixing harness issues often resolves communication loss

Replace Body Control Module (BCM) hard

Estimated Cost: $300 - $800

Requires programming to vehicle; professional service recommended

Replace blown fuses and ensure correct power/ground easy

Estimated Cost: $10 - $50

Basic step that can resolve simple communication loss causes

Common Misdiagnoses

Avoid these common diagnostic mistakes:

Interpreting symptoms as purely mechanical engine issues rather than electrical communication failure

Frequently Asked Questions

Technical definition of U0140 OBD-II Code

When your OBD-II scanner reads U0140, it means: Lost Communication With Body Control Module. This code is related to the vehicle's Sensors.

How serious is the U0140 code?

You should treat U0140 as a medium issue. May cause loss of body‑related electrical functions; can impact starting and safety systems if multiple networks fail

Common signs of the U0140 error code

You may experience the following: Check engine or warning light illuminate, Body electrical functions (lights, door locks, windows) malfunction, Erratic interior/exterior lighting.

What causes the U0140 code?

The most common causes are: Faulty Body Control Module (BCM), Damaged or loose wiring and connectors in BCM circuit, CAN bus communication failure.

Estimated repair costs for different causes of U0140

Repair costs depend on the specific failure. A simple Replace blown fuses and ensure correct power/ground replacement is relatively affordable ($10-$50), whereas a Replace Body Control Module (BCM) repair is more expensive, potentially reaching $800.

Is U0140 a generic or manufacturer-specific code?

The U0140 code is a generic powertrain code, meaning it applies to almost all makes and models, such as Honda, Toyota, VW, Ford, and Chevy.

U0140: Lost Communication With Body Control Module