OBD-II trouble code
U0140: Lost Communication with Body Control Module (BCM)
A module on the network can no longer hear from the body control module — the computer that runs lighting, locks, windows, and other body electronics. Usually a power, ground, or wiring fault at the BCM.
Quick facts
- System
- Network
- Category
- Network Communication
- Severity
- High severity
- Drivable
- No — stop driving until repaired
- Repair cost range
- $100 – $1,400
- DIY difficulty
- Shop recommended
What does U0140 mean?
U0140 is set when another module on the vehicle's communication network stops receiving messages from the body control module (BCM). The BCM is a central computer that manages the vehicle's body electronics — interior and exterior lighting, power locks and windows, the horn, wipers, anti-theft and keyless entry, courtesy lamps, and often the gateway between comfort and powertrain networks. Because the BCM is involved in so many everyday functions and frequently acts as a network hub, losing communication with it can affect a wide and seemingly unrelated set of features.
The causes are the usual communication-code set. The BCM may have lost power or ground through a blown fuse, a corroded ground, or a failed relay. The CAN wiring to the BCM may be damaged, or its connectors may be corroded or have backed-out terminals. Water intrusion is a common culprit because the BCM often lives under the dash or behind a kick panel where leaks from the windshield, sunroof drains, or HVAC can reach it. The BCM's internal circuitry can fail, or — because the BCM frequently serves as a gateway — a fault there can disrupt communication across multiple networks at once.
The symptoms depend on what the BCM controls on a given vehicle, but they're usually noticeable: erratic or dead interior and exterior lighting, power locks and windows that don't respond, keyless entry that stops working, wipers or the horn misbehaving, and warning lights on the dash. On vehicles where the BCM is the network gateway, a no-start or widespread feature loss is possible. Because the effects can be broad and a gateway BCM failure can take down other systems, U0140 should be diagnosed rather than ignored.
Common causes
- Blown BCM power fuse
- Corroded or loose BCM ground connection
- Water intrusion at the BCM (windshield, sunroof drain, or HVAC leaks)
- Damaged CAN wiring to the BCM
- Corroded or backed-out terminals at the BCM connector
- Failed internal circuitry in the BCM
- BCM acting as a failed gateway, disrupting multiple networks
- Failed BCM (after power, ground, and wiring are ruled out)
Symptoms
- Erratic or non-functional interior and exterior lighting
- Power locks, windows, or keyless entry not responding
- Wipers, horn, or courtesy lamps misbehaving
- Warning lights on the instrument cluster
- Anti-theft system activating or preventing start
- Scan tool can't communicate with the BCM specifically
- Widespread feature loss or no-start if the BCM is the network gateway
Diagnostic steps
- 1.Scan all modules and confirm the BCM is the unreachable one while others respond.
- 2.Check the BCM power and ground fuses and any related relay.
- 3.Inspect the BCM location for water intrusion — check windshield and sunroof drains and HVAC condensate paths that can leak onto the module.
- 4.Inspect the BCM connector and ground for corrosion, looseness, and backed-out terminals.
- 5.Measure CAN-High and CAN-Low at the BCM connector (rest near 2.5 volts) and verify continuity to the bus.
- 6.If the BCM is a gateway and several networks are affected, confirm power/ground/wiring before condemning the module; if those are good, the BCM likely needs replacement and programming.
Repair cost
$100 – $1,400
A blown fuse, corroded ground, or dried-out water-damaged connector repair is the cheapest fix at $100-$300. Wiring or connector repair runs $200-$600, with diagnostic time adding $150-$300. BCM replacement, including programming and any anti-theft relearn, runs $500-$1,400. Water-intrusion damage can raise costs if the leak source also needs sealing.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with module communication / can bus diagnosis preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.