Powertrain, generic · Transmission

P088A Transmission Fluid Filter Deteriorated

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Allison's 'Prognostics' in its fourth and fifth generation controls (1000 to 4000 series, buses and trucks, from 2009) has no fluid quality sensor: the gearbox module calculates. No car maker is known to use these codes. Its filter life monitor judges the pressure drop across the filter circuit; in Allison's patent a differential pressure valve operates a switch with temperature-dependent time limits. P088A, called 'filter maintenance alert' by Allison, is the early warning: the wrench symbol flashes. A faulty main valve body in some 3000/4000 units triggered it early (field action 2019FA07). After a filter change the monitor is reset by a selector sequence.

Likely causes

Filter change interval reached
Heavy contamination from clutch wear
Filter changed without resetting the monitor
Faulty main valve body (Allison serial range)

Symptoms

  • Wrench or TRANS SERVICE indicator flashing
  • Usually no change in driving behaviour

Repair estimate

DifficultyEasyDIY possible
Parts and labour€60–250
Time0.5–1.5 h

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

Parts involved

transmission fluid filtertransmission fluidtransmission control module

Related codes

P088BP0897P0218P0711

References: static.nhtsa.gov, static.nhtsa.gov, patents.google.com, gearsmagazine.com.