U0140 code: Lost Communication With Body Control Module
U0140 means lost Communication With Body Control Module. The code says where to look, not what failed — the fix depends on which cause your car actually has.
What U0140 means
U0140 means other computers lost contact with the body control module (BCM) — the computer that runs things like lights, wipers, power windows, locks, and often key/security functions. As with all U-codes this is a network fault, not proof the BCM is dead: check for blown fuses or a lost power feed to the module, corroded connectors and grounds, and damaged network wiring before suspecting the module itself. Low battery or charging voltage is a classic cause of phantom communication codes and is the first, free check. Symptoms can be strange and scattered — flaky interior electronics, warning lights, sometimes security-system quirks that prevent starting — because the BCM touches so many small systems. Diagnosis means confirming the BCM has power, ground, and an intact data connection.
U0140 symptoms
- Erratic behavior of lights, wipers, locks, or windows
- Multiple warning lights on the dash
- Security/immobilizer quirks, sometimes a no-start
- Other lost-communication codes stored alongside
What it costs to fix U0140
Varies by vehicle — get it diagnosed.
The repair cost for this code depends too much on your exact vehicle and the underlying cause to quote a meaningful range. Confirm the cause first so you only pay for the fix you actually need.
Diagnose U0140 for my vehicle →How to fix U0140
Advanced — usually a shop job unless you’re well equipped
- Charge the battery and check for a drain
Bring the battery to full charge and confirm normal charging voltage. Because the body module stays partly awake after the car is locked, a BCM that won't go to sleep can flatten the battery overnight — so if the battery keeps dying, measure parasitic draw as part of this diagnosis rather than just buying another battery.
- Check every BCM power feed and ground
Body modules often have several feeds — constant battery, ignition, and accessory — spread across the interior and underhood fuse boxes, plus one or more ground points behind the kick panel or dash. Check each fuse with a test light key on and key off; one missing feed can leave the BCM half-working and intermittently off the network.
- Look for water around the module
The BCM usually lives under the dash, behind a kick panel, or built into the interior fuse block. Feel the carpet and insulation underneath for dampness — a leaking windshield cowl, blocked sunroof or A/C drain, or a bad door seal can soak the module's connectors. Corroded pins need cleaning or repair, and the leak needs fixing too.
- Disconnect aftermarket alarms and remote starters
Add-on security systems, remote starters, and some trackers are commonly spliced into wiring at the BCM. A poor splice or a failing add-on can corrupt traffic or disrupt the BCM, so unplug or bypass anything aftermarket and see whether communication returns before blaming the factory module.
- Test the network connection, then replace and program if confirmed
With power and ground proven, check the CAN high and low wires at the BCM connector against the wiring diagram for opens, shorts, and normal voltage. Only then consider a new BCM; it almost always needs programming, and on many cars the key and immobilizer setup must be redone, which can require dealer-level access.
DIY or shop? U0140 has a high DIY payoff in its early steps: a weak battery, a blown feed fuse, a wet footwell, or a sloppy remote-start install can all be found and fixed at home with a test light and some patience. It becomes shop work once suspicion moves to the network wiring or the BCM itself, because replacing a body module typically involves programming, vehicle configuration, and often key or immobilizer relearning that a generic scan tool can't do. A used BCM pulled from another car rarely works without that same setup.
Tools for the DIY steps: Test light · Digital multimeter with a milliamp range · Trim panel removal tools · Full-system scan tool · Contact cleaner
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for U0140.
Start a case with U0140 and your car. Redline weighs these causes against what your car shows, and names the check that would settle it before you buy parts.
Can I drive with U0140?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
U0140: common questions
Can I drive with U0140?
A code by itself can't answer that. Check that your lights and wipers work — if they don't, don't drive it. The risks are losing convenience and visibility systems, and on some cars security functions can interfere with starting. Get it diagnosed promptly.
What does the body control module actually do?
It's the computer behind most non-engine electrics: exterior and interior lights, wipers, power windows and locks, and often the security/immobilizer system. That's why symptoms of losing it look like scattered electrical gremlins rather than an engine problem.
Is U0140 an expensive fix?
It depends entirely on the cause. A fuse, ground, or connector is cheap; harness repairs are moderate; a replacement BCM with programming is the costly end. Diagnosis has to sort that before anyone can quote fairly.
Should I check my battery first?
They can — weak batteries and poor grounds are notorious for causing phantom lost-communication codes across multiple modules. Verify battery and charging voltage before spending anything on parts.
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like U0140 from your phone. See our guide to the best OBD2 Bluetooth adapters. Run a repair shop? See Redline for shops.
Generic OBD-II reference. Manufacturer-specific behavior varies. Confirm with a scan tool and, for safety-related codes, a professional inspection. Cost ranges are reference ranges, not quotes.
Seeing U0140 on your car?
Every problem becomes a Case. Tell Redline what the car is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.