P27A7Pressure Control Solenoid A Data Incompatible
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P27A7 means the transmission controller holds no usable calibration curve for pressure control solenoid A. Each valve body is measured at the factory, and GM writes its current-to-pressure data into TCM memory; at every start-up the module checks that record. GM's 2020 table 20OBDG04 flags it when the data are missing after a replacement or brand-new TCM is fitted, belong to another solenoid class, fail the checksum, or contain axis points that fall instead of rise, rated Type A after one trip. On the nine-speed valve A is line pressure, on the ten-speed clutch C1, on the CVT the secondary pulley; the 2019 hybrid table 19OBDG01 lists it in the HPC1 too. The MIL comes on, and shifting is usually rough until the data are reprogrammed.
- What you may notice
- MIL on right after start-up
- Harsh engagements or firm shifts from imprecise line pressure
- Transmission may run a substitute program
- Likely causes
- LikelyNew or service TCM installed without loading the solenoid characterization data
- LikelyValve body replaced but the data for its part number not written to the TCM
- PossibleData set for a different solenoid class or valve body entered
- RareProgramming aborted, leaving a corrupted block (checksum error)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €100 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.