Powertrain, generic (extended)

P2681 Engine Coolant Bypass Valve A Control Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

Bypass valve A is an electrically driven coolant valve whose role differs by maker. P2681 flags an open or otherwise faulty drive circuit. GM's 2011 Volt table checks it in the HPC2/VICM: 40 failures in 50 samples at 100 ms, Type B. Ford's 2020–2023 gasoline summary defines valve A as the automatic transmission cooler flow (transmission warm-up) valve and sets the code when its smart driver reports a fault for 5 s. Toyota bulletin T-SB-0112-24 (A25A and M20A engines, 2018–2021) replaces the water valve for P2681 subtypes 11 (circuit grounded) and 15 (open circuit or battery short). Ram 1500 3.6 L trucks needed a new three-way coolant valve with a cracked gear (07-005-24); VW reflashed 2024 Atlas engine controllers.

Likely causes

Failed bypass valve (motor, gear or electronics)
Chafed harness or open fuse in the valve supply
Loose or corroded valve connector
Engine control software causing false detection

Symptoms

  • Check engine light on
  • Slow warm-up of engine or transmission
  • Maintenance or temperature warning message

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–700
Time0.5–2.5 h

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

Parts involved

coolant bypass valve asolenoidwiring harness

Related codes

P2682P2683P26A3P26A6P26ACP26B7

References: gsi.ext.gm.com, fordservicecontent.com, static.nhtsa.gov, static.nhtsa.gov.