Powertrain, generic (extended)

P2680 Coolant Degassing Valve Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2680 is the high-voltage fault of the degassing valve drive: the controller cannot pull the line down, so the valve stays in its unpowered state whatever is commanded. A wire touching a battery feed, an internally open solenoid, or a defective output transistor are the classic reasons. Because degassing only works when bubbles can reach the expansion tank, where the coolant calms and releases trapped gas, a valve stuck in the wrong state may leave air in the engine circuit or slow warm-up, depending on its default. No manufacturer documents P2680 publicly, and no threshold is published. The monitoring duty comes from CARB's comprehensive component rules. Check the coolant level and look for overheating signs.

Likely causes

Control wire shorted to a battery feed
Internally open solenoid of the degassing valve
Defective output stage in the control module

Symptoms

  • Check engine light or stored code
  • Air pockets, gurgling or weak cabin heat
  • Temperature gauge higher than usual

Repair estimate

DifficultyMediumDIY possible
Parts and labour€40–400
Time0.5–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

coolant degassing valvesolenoidwiring harness

Related codes

P2678P2679

References: law.cornell.edu, mahle-aftermarket.com.