Powertrain, generic (extended)

P2E81 Cold Start Engine Coolant Bypass Valve D Stuck Closed

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P2E81 is the cold-start version of P26C2 for valve D, which GM uses as the block rotary valve between two mechanical end stops. Its 2025 ECM tables (25OBDG03B) count a failure when commanded and measured position differ by more than 5° while raw feedback stays below 50°, i.e. on the closed side, in 4 of 5 seconds; Type B, MIL after two trips. It only runs in low-flow coolant mode (also with auto-stop) and with catalyst warm-up active, at 11 V or more, with block coolant above −34 °C and no calibration run for 37 s. CARB asks that faults found during the cold-start strategy carry their own codes. Keeping coolant still in the block is intended at first, as a Ford patent explains, but a valve that will not open later risks hot spots. The open side is P2DE8.

Likely causes

Block rotary valve stuck on the closed side (deposits, wear)
Valve actuator too weak to turn the valve when coolant is cold and thick
Chafed or corroded harness to the valve actuator
Invalid end-stop learn values after repair or battery disconnect

Symptoms

  • Check engine light after two trips
  • Engine temperature rising faster or unevenly after a cold start
  • Usually no driveability change

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€150–900
Time1–4 h

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

Parts involved

coolant bypass valve d

Related codes

P2DE8P26C2P26C0P2DE7P2E82

References: gsi.ext.gm.com, law.cornell.edu, image-ppubs.uspto.gov.