U0140 – Lost communication with body control module (BCM) missing message

Last updated: April 11, 2026

U0140 means one or more modules on the vehicle network stopped receiving the body control module’s messages. In plain English, the car may lose body-related functions such as power locks, interior lights, wipers, warning chimes, or keyless entry, and a scan tool may not talk to the BCM at all. This U0140 code does not prove the BCM failed. It tells you a control module detected a missing message on the network. According to factory diagnostic data across many brands, this definition stays intentionally general, so testing must identify whether the problem comes from BCM power, ground, connectors, wiring, or the communication bus itself.

🔍Look up your vehicle's recalls, specs & safety ratings — free VIN decoder with NHTSA data

U0140 Quick Answer

U0140 points to lost communication with the body control module, not an automatic BCM failure. Check whether the BCM appears on a full network scan first, then verify BCM power, ground, and network circuit integrity.

What Does U0140 Mean?

The official U0140 meaning is lost communication with body control module missing message. Another module set this code because it expected data from the BCM and did not receive it. In practice, that means body functions may stop working, work intermittently, or trigger several warning messages at once. The exact effect depends on the vehicle, because the BCM manages different features on different platforms.

Technically, the setting module monitors network traffic and looks for expected BCM messages within a set time window. With the SAE J2012DA FTB suffix -87, the subtype points to a missing message condition. That means the issue centers on absent network data, not a proven internal BCM failure. Diagnosis must confirm whether the BCM lost power or ground, dropped off the CAN or LIN network, has connector damage, or sits on a faulted bus segment that blocks communication.

Theory of Operation

Under normal conditions, the BCM acts as a major network participant and often as a gateway for body-related data. It exchanges status messages with other modules over the vehicle communication network. Those messages can include door status, ignition mode, theft deterrent status, lighting requests, wiper commands, retained accessory power, and key or immobilizer information. Other modules depend on those messages to make decisions and to coordinate features across the vehicle.

This code sets when a module no longer sees the BCM’s expected traffic. That can happen if the BCM loses battery feed, ignition feed, or ground. A damaged connector can interrupt both power and data at the same time. Network wiring faults can also block BCM messages, especially if a shorted module or damaged CAN pair drags the bus down. Because U-codes are intentionally broad by design, the code identifies a communication problem area. It does not identify the root cause by itself.

Symptoms

U0140 symptoms usually involve scan tool communication problems first, followed by body function failures that match the BCM’s role on that vehicle.

• Scan tool issue: The BCM may not appear on the module list, may show “no response,” or may drop in and out during a network scan.
• Body functions inoperative: Power locks, windows, interior lamps, chimes, or remote entry may stop working or work only sometimes.
• Multiple warning messages: The cluster may display several unrelated warnings because other modules lost BCM data they need.
• No crank or start authorization issue: Some vehicles route theft deterrent or ignition mode information through the BCM, which can block starting.
• Wipers, lighting, or horn faults: Exterior lighting, wiper operation, turn signals, or horn control may act erratically or stay disabled.
• Battery drain complaint: A BCM or network that stays awake after key-off can create a parasitic draw and a dead battery.
• Intermittent accessory operation: Retained accessory power, radio wake-up, or power outlet operation may behave unpredictably.

Common Causes

• BCM power feed loss: A blown fuse, weak fuse connection, or failed power distribution path can shut the BCM down so other modules stop receiving its expected messages.
• BCM ground circuit resistance: Corrosion or a loose ground eyelet can let the BCM power up poorly or reset, which interrupts network communication and triggers a missing message fault.
• Open or short on the CAN network: A damaged CAN+ or CAN- circuit can block BCM messages from reaching the rest of the network even when the BCM itself still has power.
• Connector spread terminals or corrosion at the BCM: Poor terminal tension or moisture intrusion can create intermittent contact at power, ground, or communication pins and cause U0140 to set.
• Water intrusion in the body electronics area: Leaks near the dash, kick panel, or junction block can corrode BCM connectors and splice packs, which disrupts message traffic on the network.
• Another module pulling the bus down: A failed networked module on the same bus can short the communication circuit and make the BCM appear offline even though the BCM is not the root cause.
• Recent battery, collision, or accessory work: Harness movement, left-loose grounds, or pin damage after prior repairs often opens the BCM communication path or its power supply.
• Low system voltage or unstable ignition feed: A weak battery, charging fault, or intermittent ignition feed can make the BCM reboot and miss scheduled messages long enough for other modules to log U0140.
• Internal BCM fault: The BCM can stop transmitting valid network messages if its internal electronics fail, but you must verify powers, grounds, and bus integrity first.

Diagnosis Steps

Use a capable scan tool with a full network scan, wiring diagram, DVOM, and preferably a lab scope. Record freeze frame and all network DTCs first. For U0140, focus on ignition state, vehicle speed, battery voltage, and related communication codes. Freeze frame shows when the code set. A scan tool snapshot helps catch an intermittent dropout during a road test.

1. Confirm U0140 with a full vehicle scan. Record whether the code is pending, confirmed, current, or history. Note every module that reports U0140 and check whether the BCM appears on the scan tool network list at all. Review freeze frame for ignition state, vehicle speed, battery voltage, and companion U-codes.
2. Check power distribution before you touch the BCM connector. Inspect BCM fuses, ignition feeds, and main body power supplies. On a communication code, also verify module presence on the network scan here. If the BCM is missing from the list, suspect power, ground, or network integrity before condemning the module.
3. Verify BCM power and ground under load. Do not rely on continuity alone. Load the circuit and run voltage-drop tests at the BCM. Ground drop should stay below 0.1 volt with the circuit operating. A high-resistance ground can pass a no-load check and still crash BCM communication.
4. Inspect BCM connectors, nearby splice packs, and harness routing. Look for backed-out pins, spread female terminals, water tracks, green corrosion, aftermarket splices, and damage from prior dash or body work. Pay close attention to kick panel and junction block areas, because that is where many BCM faults start.
5. With ignition ON, check CAN bias voltage to ground at an accessible module or DLC when the network is powered. On a healthy high-speed CAN bus, CAN+ and CAN- both bias near 2.5 volts to ground. Ignition-off readings do not provide a valid bias reference.
6. Turn ignition OFF and disconnect the battery before resistance testing. Measure resistance between CAN+ and CAN- at an accessible module connector or the DLC if the circuit design allows it. A healthy terminated bus reads about 60 ohms. Around 120 ohms or OL points toward an open path or missing termination.
7. If resistance or bias voltage looks wrong, isolate the faulted section. Disconnect suspect modules one at a time only after you identify the correct network branch from the wiring diagram. Watch for the bus to recover and for the BCM to reappear on the network scan. This step finds a module that pulls the bus down.
8. If the BCM communicates intermittently, use a scan tool snapshot during a wiggle test or road test. Freeze frame captured the conditions when the DTC set. Snapshot data captures the dropout live. Move the harness near the BCM, fuse block, door sill, and known body splice locations while monitoring module communication status.
9. Once communication returns, clear codes and perform a full network rescan. Confirm that the BCM now reports normally, no related U-codes reset, and body functions operate correctly. Verify door locks, interior lighting, warning chimes, retained accessory power, and any other BCM-controlled features affected on that vehicle.
10. If every power, ground, connector, and network test passes, follow the service information for BCM pin checks, setup, and programming requirements. Only then consider BCM replacement. Many vehicles require configuration or theft relearn after BCM service, so you must prove the circuit first.

Professional tip: U0140 often shows up as a victim code in several modules. The module that logs U0140 usually did not fail. Find out whether the BCM is truly offline or whether another module is collapsing the bus. Network scan results, loaded power and ground tests, and CAN resistance checks will save you from an expensive wrong call.

Possible Fixes

• Repair the BCM power supply circuit: Replace the failed fuse, correct the loose fuse terminal, or repair the open power feed that prevented the BCM from staying online.
• Clean and tighten BCM ground connections: Remove corrosion, restore metal-to-metal contact, and secure the ground point if voltage-drop testing proved excessive resistance.
• Repair damaged CAN wiring: Fix the open, short, rubbed-through section, or poor splice in the CAN+ or CAN- circuits if bus resistance or bias voltage tests showed a network fault.
• Repair or replace corroded BCM connectors and terminals: Restore proper pin tension and terminal contact if inspection found moisture damage, spread terminals, or backed-out pins.
• Correct water intrusion and harness damage: Seal the leak source and repair affected wiring or splice packs if water entered the BCM or body harness area.
• Replace the module that is pulling the network down: If isolation testing proves another control unit collapses the bus, repair that module or its branch circuit rather than replacing the BCM.
• Replace and program the BCM only after circuit proof: If the BCM has correct power, ground, and network integrity but still fails to communicate, BCM replacement and setup may be required.

Can I Still Drive With U0140?

You may be able to drive with U0140, but you should not assume the vehicle is fully safe or fully functional. This U0140 code means one or more modules stopped receiving the BCM message they expect. On many vehicles, the BCM manages body functions such as exterior lighting, wipers, retained accessory power, keyless entry, warning chimes, door locks, and theft deterrent logic. Some platforms also route ignition mode status and wake-up information through the BCM. If communication drops out while driving, you may see multiple warning lights, inoperative accessories, no-crank issues after a key cycle, or erratic electrical behavior. If the vehicle has lighting faults, security faults, or intermittent starting problems, limit driving until you test it. If the car runs normally and the problem only affects convenience features, the risk is lower, but the fault can still worsen without warning.

How Serious Is This Code?

U0140 ranges from moderate to serious, depending on what the BCM controls on that vehicle. In the mild case, it acts like an inconvenience. You may lose power locks, interior lights, remote functions, or scan tool access to the BCM while the engine still runs fine. In the more serious case, the BCM communication loss disrupts lighting, wiper operation, ignition state reporting, theft deterrent functions, or gateway traffic between modules. That can create a no-start, a stall after a restart event, or unsafe visibility problems in rain or at night. The code itself does not prove the BCM failed. It only proves another module did not receive the expected message. Ignoring it often leads to repeat dead-battery complaints, intermittent no-crank conditions, and expensive guesswork when the real problem is a poor power feed, ground, connector, or CAN network fault.

Common Misdiagnoses

Technicians often misdiagnose U0140 by condemning the BCM as soon as the scan tool cannot talk to it. That shortcut wastes money. A dead BCM can set this code, but so can a blown BCM feed fuse, a weak ground, water intrusion at a connector, aftermarket alarm wiring, or a shorted module pulling the network down. Another common mistake is reading only one module and ignoring the full network map. You need to see which modules report U0140, which modules still communicate, and whether the BCM appears online, offline, or intermittently present. Shops also miss voltage-drop testing under load. A corroded ground may pass a quick continuity check and still fail in operation. The right path starts with network presence, then power and ground integrity, then bus condition, and only then module replacement or programming decisions.

Most Likely Fix

The most common U0140 repair direction is restoring BCM power, ground, or network integrity rather than replacing the BCM first. In real-world cases, technicians frequently find a poor body ground, a loose BCM connector, water-damaged terminals, a blown feed fuse, or wiring damage near kick panels, fuse blocks, or prior aftermarket splices. If those checks pass, the next likely repair direction is isolating a CAN fault or confirming a BCM that drops offline after its circuits prove good. After any repair, clear the code, perform a full network scan, and drive the vehicle through the conditions that originally set the fault. Enable criteria vary by platform, so service information must confirm when the communication monitor has run and passed.

Repair Costs

Network and communication fault repairs vary by root cause — wiring/connectors are often the source, but module-level repairs or replacements can be significantly more expensive.