U0140 on Toyota: How to Diagnose & Fix
Lost Communication with BCM
1 Toyota model · 1 documented issue · $250-$900 repair
U0140 on Toyota by model: symptoms, diagnosis and fix
Multiple owners of the new U.S.-market 2024+ Land Cruiser have reported weak 12-volt batteries, repeated jump-starts, or complete no-start conditions after the vehicle sits for relatively short periods. Reports often mention telematics, accessory modules, or software-related parasitic draw behavior rather than a single failed starter or alternator. The issue is especially frustrating on low-mileage vehicles and can trigger a cascade of warning messages when voltage drops.
Common Symptoms
- Dead battery after sitting overnight or a few days
- Clicking or no crank
- Multiple warning lights on startup
- Need for repeated jump-starts
- Low voltage messages in app or cluster
How to Fix
Perform a battery state-of-health test and a parasitic draw test after all modules time out, then inspect for software updates or TSB guidance related to telematics/body control modules. Replace any battery that has been deeply discharged multiple times, because AGM batteries often lose capacity quickly after repeated low-voltage events. If accessories were added, isolate them before condemning factory modules.
What you need to diagnose it
The fix here starts with a test, not a part — which repair you need depends on what the test finds.This issue involves U codes, which a basic engine-code reader cannot see.At least one code uses a manufacturer-specific format. No scanner recommendation is shown because family-level coverage cannot prove it can read that code.
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Testing and isolating the fault is DIY work. Replacing or reprogramming a control module is not — most are VIN-programmed, so a new one does nothing until a shop codes it to your car. Check for an open recall or service bulletin before buying anything.
Owner tips & cautions
- TipIf the vehicle sits often, owners commonly use a smart AGM-compatible maintainer to prevent deep discharge.
Sources for this issue (1)
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 Toyota?
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 Toyota it is documented across 1 model: Land Cruiser.
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 Toyota?
Published repair estimates on Toyota range from $250 to $900 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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.