P27EC code meaning
Transmission Range Control A Position Sensor/Switch Circuit Range/Performance
Powertrain system Generic code P27xx codes Check engine light
What P27EC means
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.
P27EC at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor2 to 8 hours
- Clears after repairAfter a drive cycle
Symptoms of P27EC
- Delayed or refused shift into park, drive or reverse
- MIL on, stop-start may be disabled
- Transmission in reduced operating mode
Common causes of P27EC
- Most likelyMode valve A sticking inside the control valve body
- PossibleNo hydraulic pressure from a failed auxiliary pump during auto stop
- Less likelyMode valve A position sensor reading wrong
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Range control position sensor aValve bodyWiring harnessTCM
What each part of P27EC means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 7 | Area: transmission. |
| EC | The exact fault in that area. |
What to do next
- Note P27EC and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P27EC
What does P27EC mean?
P27EC means "Transmission Range Control A Position Sensor/Switch Circuit Range/Performance". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P27EC?
Drive gently and only to a workshop. With P27EC the car can go into limp mode (reduced power) to protect itself.
Will P27EC fail an emissions test?
Yes, it can. P27EC is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P27EC to fix?
Difficulty: workshop only. A typical repair takes 2 to 8 hours of work. This is a job for a workshop.
Will P27EC clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.