Powertrain, generic (extended)

P26A9 Engine Coolant Bypass Valve A Position Sensor Stop/Minimum Stop Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

The title refers to the learned end stop of valve A. GM's use of P26A9 shifted over time. On the 2011 Volt it covered feedback sitting in a forbidden zone (5–30 % or 70–95 %), sudden jumps above 6 % and slow drift above 3 %, all Type B. In the 2016 Volt table the VICM uses it when the valve misses its commanded position within 15 s, retries the end-position learn up to three times with 10 s each, and still fails; coolant must be above 58 °C, and GM notes that an open drive circuit also spoils the learn. The 2016 ELR section treats a failed end-position learn above 50 °C the same way. Subaru's 09-80-21 includes the P26A series. A sticking valve, deposits in the housing or a valve fitted without a relearn are typical causes.

Likely causes

Valve rotor sticking from deposits or contaminated coolant
End position not relearned after valve or module replacement
Open motor drive circuit preventing the learn routine
Drifting position sensor misreporting the stop

Symptoms

  • Check engine light after two drives
  • Engine overheats or stays too cool depending on stuck position
  • Weak or uneven cabin heat

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–900
Time0.3–4 h

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

Parts involved

coolant bypass valve aposition sensor

Related codes

P26AAP26A5P26A3P2681P26ABP26B1

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