Invalid Data from Body Control Module B
Diagnostic trouble code U0443 indicates that a control module (such as the ECM or PCM) has received invalid, corrupt, or missing data from the Body Control Module 'B' (BCM 'B') over the CAN bus. This means the data transmitted by the BCM 'B' does not meet expected parameters or contains integrity errors, preventing proper processing. The issue may stem from CAN communication faults, a faulty BCM 'B', or electrical interference.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Internal failure of the Body Control Module 'B' (BCM)
- Damaged or corroded CAN bus wiring (high/low speed)
- Incorrect resistance in CAN bus terminators
- Electromagnetic interference on communication lines
- Loose, corroded, or damaged connectors at the BCM 'B'
- Ground or voltage reference fault at the BCM 'B'
- Corrupted software or calibration in the BCM 'B'
- Fault in another control module affecting the CAN network
3. Symptoms You Will Notice
- Check Engine Light or other warning lights illuminated
- Malfunction of body-related features (e.g., power windows, locks, lights)
4. Step-by-Step Diagnosis
Scan for all stored codes and freeze frame data
Inspect CAN bus wiring and connectors for damage, corrosion, or looseness
Check CAN bus termination resistance (should be ~60 ohms with power off)
Test BCM 'B' power and ground circuits
Attempt to communicate with BCM 'B' via scan tool; if no response, suspect module failure
Check for technical service bulletins (TSBs) related to U0443
If wiring and power are good, replace BCM 'B' and reprogram if necessary
5. Frequently Asked Questions
Is it safe to drive?▼
The vehicle may still be drivable, but some body functions may not work properly. It is recommended to diagnose and repair the issue promptly to avoid further electrical problems.
How much does it cost to fix?▼
Costs vary widely: diagnosing the CAN bus can be $100-$200, while replacing a BCM 'B' (including programming) can range from $500 to $1,200 or more, depending on the vehicle.