P2678 - OBD II Trouble Code

January 31, 2017

Our automotive experts have put together the following information about the P2678 diagnostic trouble code. We've provided the common symptoms that occur when this code is set along with the frequent repairs that address the issues related to the P2678 code.

OBD II Fault Code

  • OBD II P2678

OBD-II Code Engine may overheat is defined as a Coolant Degassing Valve Control Circuit/Open

The Coolant Degassing Valve allows Coolant that has been vaporized to return to the pressurized overflow tank. If this Valve does not operate as requested by the engine computer (PCM), code P2678 will be stored.

Engine may overheat Symptoms

  • Engine may overheat

Common Problems That Trigger the P2678 Code

  • Coolant degassing valve failure
  • Engine coolant level is too low
  • Powertrain Control Module (PCM) failure
  • Wiring issue

About the Author

Brad Kava is an automotive expert at RepairPal, the leading online source of auto repair resources and estimates. With many ASE Master certified mechanics on staff who have decades of experience, RepairPal knows all the fine points of car repair.

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