U0140: How to Diagnose & Fix — Lost Communication with BCM
26 vehicles · 17 makes · $10-$2,500 repair
How to diagnose and fix U0140: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Jaguar S-TYPE · 2000–2008
The S-TYPE is notorious for electrical gremlins caused by moisture ingress into control modules and poor CAN bus connections. Phantom warning lights, inoperative features, and intermittent faults across multiple systems are common and difficult to diagnose without dealer-level equipment.
Common Symptoms
- Multiple warning lights illuminated simultaneously
- Windows or locks operating erratically
- Instrument cluster errors or flickering
- Intermittent no-start condition
- Features working one day and not the next
How to Fix
Check all module locations for moisture ingress, particularly the driver footwell and trunk. Clean and reseal all CAN bus connectors with dielectric grease. Reprogram affected modules with the latest software. Replace the 12V battery if it is over 4 years old.
Owner tips & cautions
- TipBuy an iCarsoft i930 Jaguar-specific scanner. It reads all Jaguar modules and saves thousands in dealer diagnostic fees. Essential tool for S-TYPE ownership.
Jaguar XJ · 2004–2012
The XJ suffers from cascading electrical faults caused by body control module (BCM) software glitches and CAN bus communication errors. Phantom warning lights, inoperative features, and intermittent failures across multiple systems are common, especially after battery disconnection or jump-starting.
Common Symptoms
- Multiple random warning lights illuminated
- Windows or sunroof operating on their own
- Central locking malfunction
- Instrument cluster errors
- Intermittent failure of various electrical accessories
How to Fix
Have the BCM reprogrammed with the latest JLR software at a dealer. Check all ground connections for corrosion, especially the main chassis ground behind the engine. Replace the 12V battery with a genuine Jaguar-spec AGM battery. Avoid jump-starting without a proper battery management system.
Owner tips & cautions
- TipAlways maintain the 12V battery in good condition. A weak battery is the #1 cause of BCM glitches on the XJ. Use a battery tender if the car sits for more than a week.
Honda Accord · 2018–2020
A software mismatch between the BCM and CAN controller causes intermittent or continuous communication disruptions between vehicle components. This results in various electrical system malfunctions including turn signals, hazard lights, rearview camera, door/trunk locks, ACC/LKAS systems, windshield wipers, and exterior lights.
Common Symptoms
- Turn signals and hazard lights not working
- Rearview camera display failure
- Door and trunk locks not functioning
- ACC/LKAS warning lights flashing
- Windshield wipers malfunctioning
- Exterior lights flickering or failing
How to Fix
BCM software update at Honda dealership (covered under recall). BCM module replacement in severe cases.
Sources for this issue (1)
Dodge Magnum · 2005–2008
Ford Transit · 2015–2020
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U0140 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does U0140 mean?
U0140 stands for "Lost Communication with BCM." U0140 is a network communication code meaning a module has lost communication with the body control module (BCM) over the vehicle's data bus. The BCM oversees many body and convenience functions — lighting, door locks, windows, wipers, anti-theft, and gateway communications — so losing contact with it can cause a wide range of seemingly unrelated electrical problems and warning lights. This is typically a wiring, connector, power/ground, or bus fault, or a failure of the BCM itself. Because the BCM often acts as a communication hub, this code can appear alongside other 'lost communication' codes.
What are the most common causes of U0140?
The most common causes of U0140 are: Loss of power or ground to the BCM, CAN/data bus wiring damage, short, or open circuit, Corroded, loose, or damaged BCM connectors, Blown fuse feeding the BCM, Failed body control module, Water intrusion or corrosion in the harness, Another module faulting the shared data bus. The specific cause varies by vehicle.
How much does it cost to fix U0140?
Repair costs for U0140 range from $10 to $2,500, depending on the vehicle and root cause.
Which vehicles are affected by U0140?
Au7o has documented U0140 across 26 vehicle models from 17 manufacturers: Alfa Romeo, Audi, Cadillac, Chevrolet, Dodge, Ford, GMC, Honda, Hyundai, Jaguar, Jeep, Kia, Land Rover, MINI, Mercedes-Benz, Pontiac, Toyota.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.