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U0140 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

U0140 is an OBD-II Code that refers to Lost Communication With Body Control Module

Meaning

A U0140 code is a generic communication systems diagnostic trouble code that refers to the communications circuit between the With Body Control Module and other control modules on the vehicle.

The body control module (BCM) is an electronic instrument that is a part of the vehicle’s total electrical system and controls procedures including but not limited to the tire pressure monitoring, remote keyless entry, door locks, anti-theft alarm, heated mirrors, rear window defroster, front and rear washers and wipers.

Causes

Common causes for this code include:

  • Malfunctioned Body Control Module (BCM)
  • Body Control Module (BCM) circuit poor electrical connection
  • Body Control Module (BCM) harness is open or shorted

Symptoms

The symptoms of a U0140 code are:

  • It’s not possible to start the car.
  • Some BCM capabilities are not accessible.
  • At high speeds, the engine has frequent failures.
  • The acceleration is unpredictable.
  • The car is plagued with constant blowing of fuses.

Diagnosis

To diagnose a U0140 DTC code, a technician would:

  1. Check the Body Control Module (BCM) with a Digital Multi-Meter for signs of corrosion or damaged pins
  2. Check the wire harness that goes from the Body Control Module to the car’s computer. 
  3. Check the car’s fuse panel and replace any blown fuses with a matching number.
  4. Check the instrument panel cluster (IPC) for signs of corrosion or burned pins.
  5. Check the car’s battery to ensure it has enough voltage and cold cranking amps (CCA).
  6. Connect a Scan Tool to check all communication between components.

Common mistakes

The following are some of the most common mistakes that a technician may make when diagnosing a U0140 code:

  • Not inspecting the Body Control Module
  • In an attempt to check all wires from the BCM, a technician may accidentally disconnect a wire that is important for car’s performance 
  • Not checking all the fuses in the fuse box 
  • Not replacing a blown fuse with a matching number 
  • Neglecting to check the IPC for corrosion 
  • Not connecting a Scan Tool to diagnose all vehicle components 
  • Not checking the car’s battery voltage and CCA 
  • Replacing parts that are not faulty or incorrectly

How serious is this?

A U0140 code is considered to be a serious code because if not diagnosed and repaired immediately, it can lead to a breakdown or even an accident. 

A U0140 code helps technicians know that the vehicle is experiencing problems with one of its modules. This helps them prioritize what needs attention first. 

A U0140 DTC code is not considered to be a critical system and can be diagnosed and repaired in a timely manner.

What repairs can fix the code?

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The following are solutions that may fix this problem:

  • Replace the Body Control Module (BCM)
  • Repair or replace the damaged harness 
  • Replace Bad fuse
  • Check the Body Control Module (BCM) connectors for corrosion and clean with a wire brush as necessary. 
  • Repair or replace the damaged wiring and connections
  • Replace Blown Fuse with a matching number

Related codes

A U0140 is related to and may be accompanied by the following codes:

C0040, P0366, P0551, P0406, P0014, P0620, P0341, C0265, P0711, P0107, P0230, P2509

Conclusion

In conclusion, the U0140 code is a communication error between the Body Control Module and other control modules on the car. When a U0140 DTC code appears, it’s usually accompanied by several other codes to help diagnose what needs attention first. A technician may not always be able to determine the exact cause of the U0140 code from the information given but can perform a few tests that will give them enough clues to fix or replace parts as necessary. It’s important for technicians to keep in mind that a U0140 DTC code is considered to be a critical system and can should be diagnosed and repaired in a timely manner.