U0140 means other modules on the vehicle’s communication network have reported losing contact with the body control module (BCM) — the module responsible for many of the vehicle’s everyday electrical functions, including power windows, door locks, and various interior and exterior lighting. This completes the network code family on this site alongside U0100, U0101, and U0121 — but because the BCM touches so many different systems, a communication loss here often looks less like one clear fault and more like several unrelated electrical problems appearing at once, which is itself a useful diagnostic clue pointing toward the BCM rather than any single component.
What Does U0140 Mean?
Modern vehicles connect their various control modules over a shared communication network, allowing them to share data efficiently rather than needing a dedicated wire for every signal. U0140 is stored by other modules when they specifically expect to hear from the body control module and don’t — not a fault reported by the BCM about itself, but other systems noticing its absence from the conversation. The BCM typically manages door locks, power windows, interior and exterior lighting, wipers, and various other body electrical functions, which is exactly why its absence tends to produce a wide, seemingly unrelated spread of symptoms rather than one clean, isolated complaint.
Common Symptoms
- Power windows not working — see our power windows won’t work guide
- Door locks malfunctioning or not responding to the key fob or interior switches
- Interior or exterior lighting behaving unpredictably — staying on, not turning on, or flickering
- Multiple, seemingly unrelated electrical symptoms appearing at the same time — a hallmark of a BCM communication issue specifically, since one module touches so many different functions
- Check engine light or other warning lights on
Common Causes, Most Likely First
- A blown fuse feeding the body control module — the cheapest and most common cause worth ruling out first, since a module with no power can’t communicate on the network at all.
- A corroded or loose ground connection to the BCM, which can cause intermittent or complete communication loss without a fully blown fuse.
- Damaged wiring in the communication network itself (the CAN bus), affecting the BCM’s ability to transmit or receive data even with power present.
- A failing body control module itself, less common but possible after many years of service or following water intrusion.
- Low battery voltage causing the BCM to reset or intermittently drop off the network — see our normal car battery voltage guide to rule this out.
How to Diagnose It
- Check the fuse box for a blown fuse related to the body control module — consult your owner’s manual for the correct fuse location and rating.
- Test battery voltage — see our normal car battery voltage guide — since a weak battery can cause exactly this kind of intermittent module dropout.
- List every symptom you’re noticing, even ones that seem unrelated (windows, locks, lights) — the breadth of the symptom list is itself diagnostically useful for a technician confirming a BCM-wide issue rather than several separate coincidental faults.
- Have the BCM’s power and ground connections inspected if fuses and battery voltage both check out fine.
Never work under a vehicle supported only by a jack. Use axle stands on firm, level ground, chock the wheels that stay down, and leave the car in gear or Park with the handbrake on. A jack lifts; stands hold.
Possible Fixes
| Cause | Fix | Typical cost |
|---|---|---|
| Blown fuse | Replace the fuse (and find why it blew) | $5 – $50 |
| Corroded ground connection | Clean and reseal the ground | $50 – $150 |
| Damaged CAN bus wiring | Repair the affected wiring | $150 – $400 |
| Failing BCM | Replace and reprogram the module | $300 – $600 |
Can I Keep Driving With This?
Yes, generally, but keep a close eye on which specific functions are affected — losing power windows or door locks is inconvenient rather than dangerous in most cases, but get it looked at reasonably soon since a BCM communication issue can be a sign of a developing electrical fault that’s worth catching early.
When to See a Mechanic
Reasonably soon — check your fuse box yourself first, since that’s the cheapest and most common cause to rule out before anything else. More in our trouble codes section.
Frequently Asked Questions
What does U0140 mean?
It means other modules on the vehicle’s network have lost communication with the body control module (BCM), which manages functions like power windows, door locks, and various lighting.
Why does this code cause so many different symptoms?
Because the BCM touches so many separate systems at once, losing communication with it often produces a wide spread of seemingly unrelated symptoms rather than one clean, isolated complaint.
What’s the most common cause of U0140?
A blown fuse feeding the body control module is the most common and cheapest cause to check first, since a module with no power can’t communicate on the network.
Is it safe to drive with a U0140 code?
Yes, generally — losing functions like power windows or door locks is inconvenient rather than dangerous, but it’s worth getting checked reasonably soon since it can indicate a developing electrical fault.
How much does it cost to fix U0140?
Often just the cost of a fuse if that’s the cause, up to $600 if the body control module itself needs replacement and reprogramming.
