U0140 — Lost Communication With Body Control Module

Is it safe to drive with U0140?

Depends on what is affected. A single dead convenience module is fine to drive with; loss of communication with engine, braking or steering modules is not. If multiple critical systems drop out, do not drive.

Will U0140 clear itself?

Sometimes U0140 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

How much does it cost to fix U0140?

Remove interfering aftermarket device — $0–$150; Replace the faulty control module — $300–$1,500; Repair CAN wiring or connectors — $100–$400. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

What are the symptoms of U0140?

Drivers most often notice: intermittent loss of functions (gauges, windows, steering assist), modules intermittently not communicating with the scanner, no-start or intermittent starting in some cases, random, hard-to-reproduce electrical glitches.

How do I diagnose U0140 myself?

Start with a scan: confirm U0140, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the vehicle network (CAN bus) communication, and verify the suspect component against live data before buying parts.

When your OBD2 scanner pulls code U0140, it means the vehicle's network has lost contact with the Body Control Module. The Body Control Module, often abbreviated as BCM, acts as the central hub for a wide range of convenience and safety-related electrical functions throughout the car. From your dashboard gauges to power windows, the BCM keeps everything communicating smoothly over the vehicle's CAN bus network—a pair of twisted wires that carry data between all the electronic control units. When this communication line goes silent, the detecting module logs U0140 and illuminates the check engine light.

The PCM or whichever module detects this communication breakdown will not trigger U0140 based on a single momentary glitch. The fault must repeat under specific operating conditions—usually several ignition cycles—before the system considers it a genuine failure. When the code does set, the module also records a freeze frame snapshot capturing engine load, RPM, coolant temperature, and vehicle speed at that exact moment. That snapshot is your most valuable clue because it describes the exact circumstances under which the communication loss occurred.

A number of problems can produce the U0140 code, but they generally fall into a handful of categories. The most frequent culprit is corroded or damaged connector pins, particularly in regions where road salt and moisture are common. Wiring harnesses routed near the windshield cowl, door hinges, or undercarriage passages suffer from flexing and water exposure over time. Breaks or shorts in the CAN bus wiring itself—either a wire grounding out or shorting to a power source—will also kill communication instantly. Voltage problems like a weak battery or failing alternator create unstable network conditions that can mimic wiring faults. Finally, aftermarket electronics such as remote starters, alarm systems, or audio equipment sometimes inject interference onto the bus that disrupts proper messaging between modules.

Symptoms of U0140

• Power windows, door locks, or both stop responding intermittently or completely
• Dashboard gauges behave erratically or go dead
• Steering feel changes noticeably when power assist drops in and out
• The scanner cannot reach certain control modules during a network scan
• Engine cranks but refuses to start, or starting becomes inconsistent
• Multiple warning indicators illuminate simultaneously on the instrument cluster
• Electrical quirks appear and disappear without a predictable pattern

Common Causes

• Corroded or loose connectors at the BCM or along the CAN bus harness
• Physical damage to the CAN bus wiring from chafing, rodent bites, or road debris
• Water intrusion into wiring junctions located below doors or under the hood
• Aftermarket accessories incorrectly tapped into the vehicle network
• Inadequate vehicle grounds causing intermittent voltage drops
• Low battery voltage or unstable charging system output
• Complete failure of the Body Control Module itself

How to Diagnose U0140

1. Connect your OBD2 scanner and confirm U0140 is stored in memory. Record the freeze frame data before clearing anything—this information shows you exactly what engine conditions existed when communication was lost, allowing you to recreate those circumstances during testing.

2. Pull all stored and pending codes from every module on the network. Codes in other controllers often point toward the actual source of the problem. Check for any outstanding technical service bulletins specific to your make, model, and model year—manufacturers frequently publish known fixes for communication-related faults.

3. Perform a thorough visual inspection of the CAN bus wiring and connectors. Look for broken insulation, corrosion buildup, bent pins, or connectors that are not fully seated. Pay special attention to areas exposed to heat, moisture, or physical movement.

4. With the ignition off, measure the resistance between the CAN-High and CAN-Low pins at the OBD2 diagnostic port. A healthy bus will typically show approximately 60 ohms total termination resistance. Anything significantly different indicates wiring damage or a failed module on the network.

5. Run a full module scan with your scanner to identify which controllers respond and which do not. The module that fails to communicate is either the faulty device itself or exists downstream of a wiring break.

6. After addressing the suspected cause, clear all codes and complete a drive cycle that includes the conditions recorded in your freeze frame. The code must not return for the repair to be considered complete.

Repair Options and Costs

Addressing the root cause systematically keeps expenses reasonable. Removing an aftermarket device that is disrupting network traffic costs nothing in parts and runs $50–$150 in labor at most shops. Repairing damaged wiring or corroded connectors typically requires $100–$300 in labor plus minimal parts costs, bringing the total to roughly $100–$400. Replacing a failed Body Control Module is the most expensive scenario, with new or used units ranging from $150–$600 and dealer or shop programming adding another $100–$300, for a total between $300 and $1,500.

Total Repair Cost for U0140

Most U0140 diagnoses end up resolving in the $0–$400 range when the problem is wiring or connectors. The full replacement scenario pushes the ceiling to $1,500. Always confirm the actual fault before purchasing expensive control modules—many communication losses trace back to simple wiring or connector problems that a careful inspection would have revealed.

Can You Drive with U0140?

This code sits at a crossroads between minor annoyance and genuine safety concern. A BCM that simply loses its dashboard backlighting or stops controlling the horn presents no safety hazard and can be addressed at your convenience. However, when U0140 appears alongside faults in the ABS controller, Supplemental Restraint System, or power steering, losing those functions while underway creates real danger. If your vehicle exhibits multiple critical system failures simultaneously, do not continue driving—have it towed to a qualified repair facility.

Related OBD2 Codes

• U0100: Lost Communication With ECM/PCM "A"
• U0101: Lost Communication with TCM
• U0102: Lost Communication with Transfer Case Control Module
• U0103: Lost Communication With Gear Shift Module
• U0104: Lost Communication With Cruise Control Module
• U0105: Lost Communication With Fuel Injector Control Module