Powertrain, generic (extended)

P27EB Transmission Range Control A Position Sensor/Switch Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

GM uses this code on automatics with internal electronic range selection (ETRS), where hydraulic mode valves within the valve body set park, reverse, neutral and drive. Mode valve A carries a Hall position sensor. In the 2020 tables for the T87A 10-speed RWD unit, P27EB sets when the raw sensor voltage lands in an invalid band between 1.263 and 1.504 V, debounced at 0.100 s per 0.163 s window, with at least 9 V battery voltage; it is Type A, so the MIL lights on the first trip. Such a level fits neither valve state and usually means a broken signal wire or a failing sensor. Shorts are P27ED and P27EE, implausible movement P27EC; valve B has P27EF. Range changes may be limited until the cause is fixed.

Likely causes

Signal wire of the mode valve A sensor broken or loose
Hall sensor on mode valve A failing
Damaged internal transmission harness or pass-through connector

Symptoms

  • MIL on after the first trip
  • Range selection restricted or delayed

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–2,000
Time1–6 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

range control position sensor awiring harnesstcm

Related codes

P27ECP27EDP27EEP27EF

References: gsi.ext.gm.com, law.cornell.edu.