Powertrain, generic (extended)

P27F2 Transmission Range Control B Position Sensor/Switch Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

With P27F2 the TCM sees the valve B position sensor above its valid range, which GM interprets as a short to voltage on that circuit. The threshold is 2.538 V, which must persist 0.100 s in a 0.163 s sampling period; GM applies it to internal range selection in the 2018 T87A nine-speed and the 2020 rear-drive ten-speed. The 2020 table rates it Type A; in the 2018 edition the MIL entry for P27F2 is blank. With valve B unconfirmed, GM suspends the movement test P27F0. Apart from a real short, a lost sensor ground can push the reading up, so measure the ground before replacing parts. P27EE is the same fault on valve A, P27F1 the low reading and P27EF the illegal mid-band level. Shifting into neutral or drive may be restricted.

Likely causes

Valve B sensor line shorted to a voltage source
Sensor ground interrupted
Hall sensor B electronics faulty

Symptoms

  • Warning light and stored transmission fault
  • Neutral or drive selection restricted

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 bwiring harnesstcm

Related codes

P27EFP27F0P27F1P27EE

References: gsi.ext.gm.com, gsi.ext.gm.com.