Powertrain, generic · Transmission

P0988 Transmission Fluid Pressure Sensor/Switch E Circuit Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

Range/performance fault of transmission fluid pressure sensor or switch E: the signal is electrically valid but does not fit the commanded clutch state or the pressure expected from other inputs. No manufacturer documents this code publicly. GM's 6T70/6T75 family, the one public user of switch E (switch 5 on the low/reverse and 4-5-6 regulator valve), folds such plausibility checks into P0989 and P0990; its switch logic table shows which gears should pressurise the switch. Sonnax describes how these normally closed film switches in the valve body module fail through debris or delaminated films. CARB requires rationality checks of transmission inputs. Siblings: P0987 circuit, P0989 low, P0990 high.

Likely causes

Damaged or delaminated switch film, switch reacts late or not at all
Debris in the fluid holding the switch or its regulator valve
Low fluid level or real pressure deviation in the clutch circuit

Symptoms

  • Often no noticeable symptom at first
  • Shift quality worsens because adaptation stops
  • Warning light depending on manufacturer

Repair estimate

DifficultyHardWorkshop job
Parts and labour€200–1,500
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

P0987P0989P0990P0871P0876P0993

References: law.cornell.edu, saabwisonline.com, sonnax.com.