OBD-II Diagnostic Trouble Code
U0140 — Lost Communication With Body Control Module
U0140 means a module, often the ECM or cluster, lost communication with the body control module (BCM). The BCM handles lighting, locks, wipers and often anti-theft and start authorization. Loss of BCM messages can affect many systems at once.
Severity 3/5
Truck-relevant
Service this week
Severity
Service this week
Lost Communication With Body Control Module
Code
U0140
Category
Network
Subsystem
Network
Truck-relevant
Yes
What this means for truckers
U0140 (Lost Communication With Body Control Module) — the BCM (which controls lights, windows, doors, etc.) is offline. Symptoms range from one dead accessory to a cabin full of warning lights.
Before you replace parts — try this first
U0140 on the Network system is most often bcm fuse, power or ground fault — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Exterior or interior lights, wipers, locks or horn may stop working or act erratically, the cluster may show warnings, and on some trucks the engine will crank but not start due to lost security authorization. Parasitic battery drain is also possible.
Common causes
- CommonBCM fuse, power or ground fault ($50–$300)
- CommonLow battery voltage or poor battery connections ($100–$500)
- OccasionalWater intrusion into the BCM or its connectors, often from a cab leak ($300–$1200)
- OccasionalNetwork wiring or connector fault at the BCM ($150–$600)
- OccasionalFailed BCM ($500–$1800)
How to fix
Check battery, BCM fuses, power feeds and grounds
When to use: First step
Inspect BCM connectors and the area for water leaks
When to use: When corrosion or wet carpet is found
Test the BCM network wiring
When to use: When power and grounds are good
Replace and program the BCM, including security setup
When to use: When wiring checks good and the BCM will not communicate
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → 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
Frequently Asked Questions
Can I drive with code U0140?
U0140 is severity 3 — plan service within a few days. Performance is likely degraded already (you may feel reduced power, harsher shifts, or slightly worse fuel economy). Continuing to drive risks additional damage to adjacent components.
How much does it cost to fix U0140 on a commercial truck?
Total repair cost ranges $50–$1800 depending on the root cause. The cheapest fix is usually the first one listed below — BCM fuse, power or ground fault — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will U0140 fail a DOT inspection?
U0140 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between U0140 and related codes?
U0140 is closely related to: 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). These codes share the same subsystem (network) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only U0140 is set without the companions, the issue is more isolated.
How do I prevent U0140 from coming back after a repair?
For U0140 (Lost Communication With Body Control Module), prevention centers on the network system. Pay attention to ground connections at every PM — bad grounds are 70% of communication codes. Inspect harness routing for chafe points. Don't disconnect modules with the key on.