U0038: Vehicle Communication Bus B Performance
What Does U0038 Mean?
U0038 is a diagnostic trouble code indicating: Vehicle Communication Bus B Performance. This code relates to the network communication system. It has been reported in NHTSA complaints across 1 different vehicle models.
Common Causes
- 🔍 Worn or fouled spark plugs
- 🔍 Clogged or leaking fuel injector
- 🔍 Dirty or failed MAF sensor
- 🔍 Failed PCV valve
- 🔍 Sensor or control module malfunction
Real Owner Reports
From NHTSA complaint database — actual owner descriptions.
"Our battery died in April 2025. We've had this car since October 2021 with only 8 miles on it. We've replaced: The PCV valve The PCV valve tube The MAF sensor The sparks plugs 3 times which was $90 each time Replaced our battery 2 times since April 2025 3 oil changes And finally replacing our ent"
— Honda Civic owner, 04/07/2025
Source: NHTSA Complaints Database
Most Reported Vehicles for U0038
Based on NHTSA owner complaint data.
| # | Vehicle | Reports |
|---|---|---|
| 1 | HONDA CIVIC |
Frequently Asked Questions
What causes communication codes?
Can a bad battery cause network codes?
What To Do Next
Possible Fixes
- 🔧 Have the code scanned with a professional-grade scanner to read freeze frame data
- 🔧 Test the relevant sensor(s) with a multimeter before replacing
- 🔧 Check battery voltage and ground connections; inspect CAN bus wiring
- 🔧 If DIY repair isn't feasible, get a diagnostic from a trusted mechanic ($50-150)
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1
Find your vehicle above
Click your make and model for real owner reports and common causes specific to your vehicle.
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2
Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
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Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.