U0640 — Lost Communication With EVAP Fuel Vapor Temperature Sensor Circuit

What Does U0640 Mean?

U0640 is a diagnostic trouble code indicating: Lost Communication With EVAP Fuel Vapor Temperature Sensor Circuit. This code relates to the vehicle systems system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.

Symptoms of U0640

⚠️ Check Engine Light (MIL) illuminated
⚠️ No communication with EVAP Fuel Vapor Temperature Sensor Circuit
⚠️ Multiple warning lights may illuminate simultaneously
⚠️ Related system completely inoperative
⚠️ System warning light illuminated

Common Causes

🔍 CAN bus wiring fault (open or shorted) to EVAP Fuel Vapor Temperature Sensor Circuit
🔍 Power or ground supply issue to EVAP Fuel Vapor Temperature Sensor Circuit
🔍 EVAP Fuel Vapor Temperature Sensor Circuit internal failure
🔍 Water intrusion damaging module or connectors
🔍 CAN bus termination resistor fault

Frequently Asked Questions

What does U0640 mean?

U0640 indicates: Lost Communication With EVAP Fuel Vapor Temperature Sensor Circuit. The vehicle's computer has detected that the EVAP Fuel Vapor Temperature Sensor Circuit is not operating within its expected parameters and stored this diagnostic trouble code.

Can I drive with code U0640?

You can drive short distances for essential trips, but schedule a diagnosis soon. Driving with U0640 for extended periods may cause additional problems.

How much does it cost to fix U0640?

Repair costs for U0640 typically range from $80 to $800, depending on the root cause. Simple wiring or connector repairs are on the lower end, while component replacement costs more. A proper diagnosis ($80–$150 at most shops) will identify the exact cause before committing to expensive parts.

What To Do Next

Possible Fixes

🔧 Inspect CAN bus wiring to EVAP Fuel Vapor Temperature Sensor Circuit for damage
🔧 Check power and ground supply to EVAP Fuel Vapor Temperature Sensor Circuit
🔧 Replace failed EVAP Fuel Vapor Temperature Sensor Circuit

1
Find your vehicle above
Click your make and model for real owner reports and common causes specific to your vehicle.
2
Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
3
Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.

U0640: Lost Communication With EVAP Fuel Vapor Temperature Sensor Circuit