Powertrain, generic (extended)

P27AC Pressure Control Solenoid F Data Incompatible

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

P27AC reports invalid calibration data for pressure control solenoid F. On GM's 2016 eight-speed this is the line pressure solenoid, and the TCM logs the fault in one trip once the data are found unprogrammed. Later GM tables assign F to the nine-speed's C4 clutch, the ten-speed's C6 clutch and the CVT's binary pump; the 2025 table 25OBDG03A still carries the check, with the same start-up test and Type A rating. Because line pressure or pump control rides on this valve in some layouts, a bad record can affect every gear, not just one shift. Typical triggers are a replacement controller or valve body installed without the data download; a faulty solenoid coil sets circuit codes instead.

Likely causes

TCM swapped and solenoid F data never loaded

Remanufactured valve body with a new ID not entered into the TCM

Data block damaged by a voltage drop during programming

Symptoms

MIL on
Firm or soft shifts throughout when line pressure depends on valve F
Possible fixed-gear substitute mode

Repair estimate

DifficultyShop_onlyWorkshop job

Parts and labour€100–400

Time0.5–1.5 h

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

Parts involved

pressure control solenoid ftcm

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com.