Powertrain, generic · Transmission

P088B Transmission Fluid Filter Very 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. P088B is the second stage of the filter life monitor: the filter counts as heavily clogged or its change as overdue, and the CHECK TRANS lamp comes on. Isuzu names it the most common reason for that lamp on its Allison trucks, a maintenance item rather than a gearbox defect. Allison's patent allows limiting gearbox functions at this stage; the bulletins describe only the warning. Change the filter and reset the monitor.

Likely causes

Filter change overdue
Monitor not reset after the change
Increased internal wear debris
Faulty main valve body (Allison)

Symptoms

  • CHECK TRANS lamp on
  • Message to service the transmission filter
  • Rarely a gear limit

Repair estimate

DifficultyEasyDIY possible
Parts and labour€60–300
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

P088AP0897P0218P0711

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