U0638: Lost Communication With Hybrid/EV Electronics Coolant Temperature Sensor A
System
Vehicle Systems
What Does U0638 Mean?
U0638 is a diagnostic trouble code indicating: Lost Communication With Hybrid/EV Electronics Coolant Temperature Sensor A. This code relates to the vehicle systems system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.
What To Do Next
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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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3
Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.
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