P27ED code meaning
Transmission Range Control A Position Sensor/Switch Circuit Low
Powertrain system Generic code P27xx codes Check engine light
What P27ED means
P27ED tells that the Hall sensor on mode valve A of GM's internal range selection delivers almost no voltage. In both the 2018 9-speed and the 2020 10-speed RWD tables the limit is a raw value under 0.414 V for 0.100 s within 0.163 s, with at least 9 V on the battery; GM itself blames a grounded or interrupted line. The code is Type A and lights the MIL on the first trip. Because the TCM then cannot confirm whether the valve has left park, the movement check P27EC is suspended while P27ED is active. Look at the sensor connector inside the transmission and the pass-through plug. High is P27EE, the invalid middle band P27EB, and valve B uses P27F1 for the same fault.
P27ED at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P27ED
- MIL lit immediately
- Shifts out of park slow or blocked
Common causes of P27ED
- Most likelySensor signal shorted to ground in the internal harness
- PossibleSensor supply open, output collapses
- PossibleHall sensor on mode valve A failed
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 aWiring harnessTCM
What each part of P27ED 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. |
| ED | The exact fault in that area. |
What to do next
- Note P27ED 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 P27ED
What does P27ED mean?
P27ED means "Transmission Range Control A Position Sensor/Switch Circuit Low". P27ED tells that the Hall sensor on mode valve A of GM's internal range selection delivers almost no voltage. It is a generic code, so it means the same on every make.
Is it safe to drive with P27ED?
Drive gently and only to a workshop. With P27ED the car can go into limp mode (reduced power) to protect itself.
Will P27ED fail an emissions test?
Yes, it can. P27ED 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 P27ED to fix?
Difficulty: hard. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will P27ED clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.