P27ECTransmission Range Control A Position Sensor/Switch Circuit Range/Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- P27EC is GM's movement check for mode valve A of its internal range selection: after the TCM commands park, drive or reverse, the position sensor must report the new state within a set delay; the logic also watches line pressure and clutch slip. Both the 2018 nine-speed and 2020 ten-speed tables rate it Type A. Bulletins show it is often hydraulic: 21-NA-169 has the valve body replaced on low-mileage 9T45/50/60 units when P27EC or P27F0 appear with clean fluid, PIP6069 says to renew the valve body rather than the TCM on 2024 full-size trucks and SUVs with the 10L80, and 19-NA-200 notes that on the 2025 Equinox a failed auxiliary pump or harness sets P27EC before P2797.
- What you may notice
- Delayed or refused shift into park, drive or reverse
- MIL on, stop-start may be disabled
- Transmission in reduced operating mode
- Likely causes
- LikelyMode valve A sticking inside the control valve body
- PossibleNo hydraulic pressure from a failed auxiliary pump during auto stop
- RareMode valve A position sensor reading wrong
- 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: €300 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.