Quick Answer
U0B91 means: U0B91 indicates a communication failure between vehicle control modules, often the Body Control Module.
Can I drive with U0B91? Immediate attention is recommended to avoid further electrical issues.
Common Questions
What does U0B91 mean and how does it affect my car?
The U0B91 code indicates a communication failure between the vehicle's electronic modules, which can lead to malfunctioning accessories and poor vehicle performance. Addressing this issue quickly can prevent further damage and ensure your vehicle operates smoothly.
What are the most common causes of U0B91 and how much does it cost to fix?
Common causes include a faulty Body Control Module (BCM), wiring issues, and software glitches. Repair costs can vary significantly based on the root cause, ranging from $50 for a software update to $800 for BCM replacement.
Can I drive my car with U0B91 or should I stop immediately?
While you may still be able to drive your vehicle, it’s advisable to stop and diagnose the issue as soon as possible. Continuing to drive with this code could lead to more severe electrical problems.
How can I diagnose U0B91 myself using GeekOBD APP?
To diagnose U0B91 with GeekOBD APP, connect the app to your vehicle’s OBD2 port, scan for codes, and check freeze frame data for context on when the issue occurs. Look for any related codes and inspect the BCM and wiring based on your findings.
What vehicles are most commonly affected by U0B91?
U0B91 is commonly found in vehicles from manufacturers like Ford, Chevrolet, and Honda, especially models made between 2015 and 2020. Always check for any recalls or technical service bulletins (TSBs) related to your vehicle.
How can I prevent U0B91 from happening again?
Preventive measures include regular vehicle maintenance, checking wiring and connectors for wear, and keeping your software updated. Using quality parts during repairs can also help avoid future issues.
What is U0B91?
The U0B91 diagnostic trouble code (DTC) signifies a communication issue between the vehicle's control modules. This code often appears in various makes and models, including popular brands like Ford, Chevrolet, and Honda, particularly in vehicles manufactured between 2015 and 2020. When you see the U0B91 code, it generally indicates that the vehicle's Body Control Module (BCM) is unable to communicate effectively with other electronic modules in the car. This failure can result from faulty wiring, a malfunctioning BCM, or issues with the vehicle’s network communication lines. In real-world terms, if this code triggers, you might experience symptoms such as erratic electrical functions, dashboard warning lights, or even failure of certain features like power windows or locks. Ignoring this issue can lead to further complications, such as more extensive electrical problems, so it’s essential to address it promptly. It's advisable to consult a professional technician for an in-depth diagnostic, especially if you are not well-versed in automotive electronics. Regular maintenance and timely diagnostics can prevent the recurrence of this code, ensuring your vehicle runs smoothly and reliably.
System: U - Network (Communication, CAN Bus)
Symptoms
Common symptoms when U0B91 is present:
- Check engine light stays on constantly, indicating ongoing issues with vehicle communication systems.
- Power accessories like windows or locks may intermittently fail or operate erratically, causing frustration during daily use.
- Dashboard lights may flicker or malfunction, making it difficult to monitor vehicle status accurately.
- Engine may hesitate or stall unexpectedly during operation, which could pose safety risks while driving.
- Decreased fuel efficiency, which can typically result from improper electrical functioning affecting engine performance.
Possible Causes
Most common causes of U0B91 (ordered by frequency):
- Faulty Body Control Module (BCM) – most common cause with a likelihood of 45%, often due to age or electrical surges.
- Wiring issues or damaged connectors – a second common cause at around 30%, typically caused by wear, corrosion, or improper installation.
- Software glitches or outdated firmware – can lead to communication failures, which can be resolved by updating the vehicle’s software.
- Less common but serious cause includes short circuits in the communication network, which could lead to more extensive electrical damage.
- Rarely, environmental factors like water intrusion or extreme temperature changes can affect module performance and lead to the U0B91 code.
U0B91 Repair Costs
Cost Breakdown by Repair Type
BCM Replacement
Replacing the faulty Body Control Module with a new or refurbished unit.
- Total: $400 - $800
- Success rate: 85%
Wiring Repair
Repairing or replacing damaged wiring and connectors.
- Total: $150 - $300
- Success rate: 75%
Software Update
Performing an update on the vehicle’s software to resolve communication issues.
- Total: $50 - $150
- Success rate: 60%
Money-Saving Tips for U0B91
- Start with the most common and least expensive repairs first
- Use GeekOBD APP to confirm diagnosis before replacing expensive parts
- Consider preventive maintenance to avoid future occurrences
- Compare prices for OEM vs aftermarket parts based on your needs
- Address the issue promptly to prevent more expensive secondary damage
Diagnostic Steps
Professional U0B91 Diagnosis Process
Follow these systematic steps to accurately diagnose U0B91. Each step builds on the previous one to ensure accurate diagnosis.
Step 1: Step 1: Initial visual inspection - Check for obvious signs like damaged wiring, loose connections, or corrosion (5-10 minutes)
Step 1: Initial visual inspection - Check for obvious signs like damaged wiring, loose connections, or corrosion (5-10 minutes).
Step 2: Step 2: OBD2 scan with GeekOBD APP - Retrieve all codes and freeze frame data to understand the fault context (10-15 minutes)
Step 2: OBD2 scan with GeekOBD APP - Retrieve all codes and freeze frame data to understand the fault context (10-15 minutes).
Step 3: Step 3: Component testing - Use a multimeter or specific diagnostic tools to test suspected components, particularly the BCM (20-30 minutes)
Step 3: Component testing - Use a multimeter or specific diagnostic tools to test suspected components, particularly the BCM (20-30 minutes).
Step 4: Step 4: System function test - Verify proper operation after repairs and clear codes using the GeekOBD APP (10-15 minutes)
Step 4: System function test - Verify proper operation after repairs and clear codes using the GeekOBD APP (10-15 minutes).
Step 5: Step 5: Road test verification - Drive the vehicle under various conditions to confirm the repair's success (15-20 minutes)
Step 5: Road test verification - Drive the vehicle under various conditions to confirm the repair's success (15-20 minutes).
Important Notes
- Always verify the repair with GeekOBD APP after completing diagnostic steps
- Clear codes and test drive to ensure the problem is resolved
- Address underlying causes to prevent code recurrence
Real Repair Case Studies
Case Study 1: 2017 Ford Fusion BCM Replacement
Vehicle: 2017 Ford Fusion, 60,000 miles
Problem: Customer reported that dashboard lights flickered and power locks did not respond.
Diagnosis: Diagnosed U0B91 code; visual inspection revealed a faulty BCM.
Solution: Replaced the Body Control Module and reprogrammed it to the vehicle.
Cost: $700 (parts: $600, labor: $100)
Result: All electrical features functioned correctly post-repair, and the code did not reappear.
Case Study 2: 2016 Honda Civic Wiring Repair
Vehicle: 2016 Honda Civic, 50,000 miles
Problem: Customer experienced intermittent power window failures and check engine light.
Diagnosis: Found U0B91 code; inspection showed damaged wiring near the driver's side door.
Solution: Repaired wiring harness and secured connections.
Cost: $200 (parts: $50, labor: $150)
Result: Power windows operated without issues, and the check engine light remained off.