U0140 Lost Communication with BCM
The U0140 code indicates that a control module (typically the PCM/ECM or another module on the CAN bus) has lost serial communication with the Body Control Module (BCM) via the Controller Area Network (CAN) for a calibrated period. This means the BCM's periodic heartbeat messages or data frames are not being received.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Faulty or internally damaged Body Control Module (BCM)
- Open circuit, short to ground, short to battery, or short between lines on the CAN High or CAN Low bus wiring to the BCM
- Loose, corroded, pushed-back, or damaged terminals at the BCM connector
- Loss of power (B+) or ground (GND) to the BCM (blown fuses, smart fuses, or power wiring issues)
- Another module on the bus pulling down the communication network
- Software glitch or need for reprogramming of the BCM or the reporting module
3. Symptoms You Will Notice
- Check Engine Light or other warning lights illuminated
- Malfunctions in body electrical systems (windows, locks, lights, wipers, etc.)
4. Step-by-Step Diagnosis
Scan all modules for codes and verify U0140 is present
Inspect BCM connector for corrosion, damage, or loose terminals
Check BCM power and ground circuits (fuses, relays, wiring)
Test CAN bus wiring (High and Low) for opens, shorts, or resistance issues
If wiring is OK, suspect BCM internal failure or software issue; attempt reprogramming or replacement
5. Frequently Asked Questions
Is it safe to drive?▼
Driving is possible but not recommended, as loss of BCM communication can cause unpredictable electrical failures and may affect safety systems. Have the vehicle diagnosed promptly.
How much does it cost to fix?▼
Repair costs vary widely: from $50–$150 for a simple fuse or wiring repair, to $300–$800+ for BCM replacement and programming.