AutoCodes – Generic – P2678

P2678 Code - Coolant Degassing Valve Control Circuit/Open

Quick Answer

The Powertrain Control Module (PCM) monitors the Coolant Degassing Valve Control Circuit. Common causes include Faulty Coolant Degassing Valve, Coolant Degassing Valve harness is open or shorted, Coolant Degassing Valve circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P2678 indicates Coolant Degassing Valve Control Circuit/Open.
Common causes: Common causes include Faulty Coolant Degassing Valve, Coolant Degassing Valve harness is open or shorted, Coolant Degassing Valve circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 7,923

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jan 25, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
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Code P2678 Description

The Powertrain Control Module (PCM) monitors the Coolant Degassing Valve Control Circuit. The PCM sets the OBDII code when the Coolant Degassing Valve Control Circuit is out of factory specifications.

OBDII Code P2678 - Coolant Degassing Valve Control Circuit/Open - AutoCodes.com — P2678 Code - Coolant Degassing Valve Control Circuit/Open

What does this mean?

What are the Possible Causes of the DTC P2678?

Faulty Coolant Degassing Valve
Coolant Degassing Valve harness is open or shorted
Coolant Degassing Valve circuit poor electrical connection

How to Fix the DTC P2678?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P2678 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P2678 code?

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.