U0140 on Hyundai: How to Diagnose & Fix
Lost Communication with BCM
1 Hyundai model · 1 documented issue
U0140 on Hyundai by model: symptoms, diagnosis and fix
The Ioniq 5's wiring harnesses run with little clearance beneath the floor and driver's seat, leaving them vulnerable to moisture. Owners have reported that even a small interior water spill soaked the floor and seat harnesses and knocked out major systems. One widely reported Florida case ran to an ~$11,882 repair to replace both harnesses, which Hyundai and the owner's insurer both declined to cover. This is an owner-reported pattern, not a recall.
Common Symptoms
- Multiple electronic systems fail simultaneously after an interior spill or leak
- Warning lights, dead accessories, or car won't power up after water exposure
- Damp carpet/floor or water pooling under the front seats
- Corrosion found on under-floor or under-seat wiring connectors
How to Fix
No recall; repair requires replacing the affected floor and/or driver-seat wiring harnesses (often a five-figure job). Owners are advised to avoid liquid spills near the seat base, address door/liftgate seal leaks promptly, and check the floor under the front seats for water/condensation pooling.
Sources for this issue (2)
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 on a Hyundai?
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. On Hyundai it is documented across 1 model: Ioniq 5.
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 on a Hyundai?
Repair costs vary widely with the root cause and Hyundai model; each issue on this page carries its own estimate where one is published.
Looking for U0140 on a different make?
View U0140 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.