P27A7: Solenoid A characterization data does not match a valid programmed set

P27A7 concerns the characterization data stored for pressure-control solenoid A in the transmission controller. In the reviewed GM table, the named functions are GF9 line control, GR10 C1 C123456R clutch control, or CVT secondary-pulley control. Those alternatives require transmission-specific identification.

The controller checks data before normal operation

The monitor runs once at normal controller power-up, during initialization before the ordinary control loop. It fails when characterization programming is not considered complete. A vehicle does not have to demonstrate clutch slip for this startup data check to fail.

Listed causes of invalid programming include missing or incomplete data, a solenoid class inconsistent with the controller calibration, a checksum mismatch and axis points that decrease when the data must remain nondecreasing. These are different data-validation failures, not four confirmed physical solenoid defects.

Service history changes the next question

The source says characterization is originally programmed according to the installed valve-body assembly part number. Following valve-body service, the associated characterization data must correspond to that assembly. A recent controller or valve-body change therefore makes component identity and completed programming especially relevant evidence.

This does not justify indiscriminate reflashing: first establish which data set and hardware belong together using the applicable procedure. A normal electrical circuit measurement cannot prove that stored characterization is correct.

Verification should confirm accepted programming for the installed assembly and a successful subsequent initialization check. The source lists Type A, one-trip behavior but does not mandate replacing solenoid A.

Source and applicability

Confirm the vehicle, transmission variant and relevant module before applying this monitor description. GM diagnostic table, PDF page 1198. GM diagnostic table, PDF page 1199.