P2678 — Coolant Degassing Valve Control Circuit/Open

What Does P2678 Mean?

P2678 is a diagnostic trouble code indicating: Coolant Degassing Valve Control Circuit/Open. This code relates to the powertrain system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.

Symptoms of P2678

⚠️ Check Engine Light (MIL) illuminated
⚠️ Erratic Coolant Degassing Valve readings
⚠️ Related system operating intermittently
⚠️ Reduced engine performance

Common Causes

🔍 Wiring issue in Coolant Degassing Valve circuit (damaged, chafed, or corroded)
🔍 Faulty Coolant Degassing Valve connector or terminal
🔍 Failed Coolant Degassing Valve
🔍 ECM/PCM connection issue

Frequently Asked Questions

What does P2678 mean?

P2678 indicates: Coolant Degassing Valve Control Circuit/Open. The vehicle's computer has detected that the Coolant Degassing Valve is not operating within its expected parameters and stored this diagnostic trouble code.

Can I drive with code P2678?

You can drive short distances for essential trips, but schedule a diagnosis soon. Driving with P2678 for extended periods may cause additional problems.

How much does it cost to fix P2678?

Repair costs for P2678 typically range from $80 to $300, 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 and repair Coolant Degassing Valve wiring and connectors
🔧 Replace faulty Coolant Degassing Valve

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.

P2678: Coolant Degassing Valve Control Circuit/Open