OBD-II Code U0140 — Lost Communication with Body Control Module

What Does This Error Mean?

U0140 means your car's computer network has lost communication with the Body Control Module (BCM). The BCM controls many convenience features: door locks, windows, interior lights, wipers, horn, and remote keyless entry. When the BCM drops off the network, any of those systems can stop working. Your car will usually still start and drive, but you may find multiple features suddenly not working at the same time. This code is often accompanied by other communication or electrical codes.

Affected Models

All CAN bus vehicles (2004+)
Very common in GM cars and trucks
Common in Chrysler, Dodge, and Jeep vehicles
Common in Ford and Lincoln vehicles
Common in Buick and Cadillac

Common Causes

Failed Body Control Module that has stopped communicating on the network
Blown fuse or bad power supply to the BCM
Corroded BCM ground connection causing communication failure
Water damage to the BCM — often located under the dash near the footwell
Battery voltage spike from jump-starting or alternator surge that damaged the BCM

How to Fix It

Disconnect the battery for 15-20 minutes to reset all modules. Reconnect, clear the codes, and test all affected systems. A power reset solves BCM communication glitches more often than you'd expect.

If codes return within a short drive, proceed to electrical inspection.
Check all BCM-related fuses. The BCM typically has one or more dedicated fuses in both the underhood fuse box and the interior fuse panel. Consult your owner's manual for the exact locations — they're labeled BCM or BODY CTRL.

Also check for any corroded or heat-damaged fuse sockets. A fuse that looks intact can sometimes have a poor connection.
Locate the BCM and inspect for water damage. In most vehicles it's under the driver-side dashboard, sometimes behind the kick panel. Look for rust staining, water marks, white mineral deposits, or swollen circuitry visible through a vented cover.

A leaking door seal, blocked sunroof drain, or faulty windshield seal can direct water right to the BCM location.
Inspect the BCM's wiring connectors. Disconnect each one, look for green corrosion or pushed-back pins, and clean with electrical contact cleaner. Reconnect firmly and check that the locking tabs click into place.

BCM connectors on high-mileage vehicles often have corroded pins that create intermittent faults.
If cleaning and reset don't help, take the vehicle to a shop with a factory-level scan tool. They can attempt two-way communication with the BCM. If it doesn't respond at all, replacement is required. Ask specifically about remanufactured units to save money.

On some GM vehicles, the BCM can be repaired by a specialty electronics shop for $150-$250 instead of buying a new one.

When to Call a Professional

BCM replacement requires programming to your vehicle's VIN and options. An unprogrammed BCM won't know what features your car has, and the theft deterrent system requires programming to accept the new module. This is a dealer or specialty shop job. Expect $100-$200 for diagnosis and $300-$800 for BCM replacement and programming.

Frequently Asked Questions

What stops working when the BCM fails?

It varies by vehicle, but typically: remote keyless entry, interior lights, power door locks, power windows, wipers, horn, and the theft deterrent system. Some vehicles also lose the ability to start because the BCM handles immobilizer functions. If five or more convenience features die at once, the BCM is a top suspect.

Can a bad BCM drain my battery?

Absolutely yes. A failing BCM can get stuck in an active state after you park, causing what's called a parasitic drain. This slowly kills your battery overnight. If you keep finding a dead battery in the morning with no obvious cause, ask a shop to do a parasitic draw test.

Can I replace the BCM myself?

You can physically swap it yourself if you're comfortable removing dashboard trim. However, the new BCM must be programmed to your vehicle before it will work. This programming step requires dealer tools or a locksmith with the right software. Without programming, the car may not start and features won't work.