U0142 Lost Communication with BCM 'B'
The U0142 code indicates that a control module (typically the PCM, gateway, or instrument cluster) has lost serial data communication with the Body Control Module 'B' (BCM 'B') over the vehicle's communication bus (CAN, LIN, etc.). This means the expected periodic messages from the BCM 'B' were not received within a calibrated time, disabling functions managed by that module.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Open circuit, short to ground, or short to battery in the CAN High or Low bus wires to the BCM 'B'
- Internal failure of the BCM 'B' module
- Loss of power (B+) or ground at the BCM 'B'
- Damaged, loose, or corroded connectors at the BCM 'B' or data bus
- Fault in the module reporting the code (rare)
- Software error or need for reprogramming of the BCM 'B'
3. Symptoms You Will Notice
- Malfunction Indicator Lamp (MIL) illuminated
- Inoperative body functions such as power windows, locks, or interior lights
- Erratic behavior or failure of systems controlled by the BCM 'B'
4. Step-by-Step Diagnosis
Scan for other related codes and check freeze frame data
Inspect BCM 'B' connectors and wiring for damage, corrosion, or loose connections
Test power and ground circuits at the BCM 'B'
Check CAN bus resistance and voltage at the BCM 'B' connector
Perform a network communication test to isolate the fault
If wiring and power are OK, suspect a failed BCM 'B' or software issue
5. Frequently Asked Questions
Is it safe to drive?▼
The vehicle may still be drivable, but some body functions may be inoperative. It is recommended to diagnose and repair promptly to avoid further issues.
How much does it cost to fix?▼
Diagnosis typically costs $100-$150. Repair costs vary: a wiring repair may be $100-$300, while replacing a BCM can range from $400 to $800 including programming.