Powertrain, generic · Transmission

P0989 Transmission Fluid Pressure Sensor/Switch E Circuit Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

Pressure switch E reads low, meaning no pressure, when it should show pressure. GM's 6T70/6T75 family uses E for switch 5 on the R1/4-5-6 clutch regulator valve; the normally closed switch sees pressure while both the low/reverse and the 4-5-6 clutch are released. The module counts clutch releases after which the signal stays low, checked with commanded clutch pressure at 50 kPa or less: 18 counts in GM's 2011 tables and on the Saab 9-4X, 17 in the 2016 table. It is a Type C or Special No Trip code without MIL, and the adaptations of both clutches are frozen. Sonnax lists P0989 among typical switch failures in this valve body module. P0990 is the stuck-high counterpart; switches A to D use P0840 to P0878.

Likely causes

Damaged or delaminated film in switch 5 of the valve body module
Debris keeping pressure away from the switch
R1/4-5-6 clutch regulator valve sticking
Low fluid level

Symptoms

  • No warning light, code stored only
  • Shifts into 4th to 6th or reverse gradually less smooth
  • Occasional limp mode if the fault persists

Repair estimate

DifficultyHardWorkshop job
Parts and labour€300–1,500
Time1.5–5 h

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

Parts involved

tfp sensor ewiring harnesstcm

Related codes

P0987P0988P0990P0969P0872P0877

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