U0664 — Lost Communication With Rear HVAC Air Cutoff Actuator

What Does U0664 Mean?

U0664 is a diagnostic trouble code indicating: Lost Communication With Rear HVAC Air Cutoff Actuator. 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 U0664

⚠️ Check Engine Light (MIL) illuminated
⚠️ No communication with Rear HVAC Air Cutoff Actuator
⚠️ Multiple warning lights may illuminate simultaneously
⚠️ Related system completely inoperative
⚠️ System warning light illuminated

Common Causes

🔍 CAN bus wiring fault (open or shorted) to Rear HVAC Air Cutoff Actuator
🔍 Power or ground supply issue to Rear HVAC Air Cutoff Actuator
🔍 Rear HVAC Air Cutoff Actuator internal failure
🔍 Water intrusion damaging module or connectors
🔍 CAN bus termination resistor fault

Frequently Asked Questions

What does U0664 mean?

U0664 indicates: Lost Communication With Rear HVAC Air Cutoff Actuator. The vehicle's computer has detected that the Rear HVAC Air Cutoff Actuator is not operating within its expected parameters and stored this diagnostic trouble code.

Can I drive with code U0664?

You can drive short distances for essential trips, but schedule a diagnosis soon. Driving with U0664 for extended periods may cause additional problems.

How much does it cost to fix U0664?

Repair costs for U0664 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 Rear HVAC Air Cutoff Actuator for damage
🔧 Check power and ground supply to Rear HVAC Air Cutoff Actuator
🔧 Replace failed Rear HVAC Air Cutoff Actuator

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.

U0664: Lost Communication With Rear HVAC Air Cutoff Actuator