Powertrain, generic (extended)

P27AD Pressure Control Solenoid G Data Incompatible

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

P27AD flags the stored data for pressure control solenoid G as not matching the hardware. GM's 2016 eight-speed table names G the torque converter clutch solenoid and sets the code in one trip. In the 2017 to 2020 tables G is clutch C5 (C57R) on the nine-speed, the line pressure valve on the ten-speed and, only on CVTs with electronic range select, mode valve A; there it is a Type A fault checked at controller start. The 2025 table 25OBDG03A no longer lists G, ending its characterization checks at F. When the line pressure valve of a ten-speed is affected, shift feel can change across all gears. Reloading the valve body data with a scan tool is the usual repair.

Likely causes

Solenoid G data missing after TCM programming

Valve body changed without matching data

TCM calibration for a different transmission variant

Symptoms

MIL illuminated
Converter clutch or range mode problems, depending on transmission
General shift harshness on ten-speed units

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 gtcm

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