P088ATransmission Fluid Filter Deteriorated
- Generic OBD-II code · Powertrain
- How the car detects it
- 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.
- What you may notice
- Wrench or TRANS SERVICE indicator flashing
- Usually no change in driving behaviour
- Likely causes
- LikelyFilter change interval reached
- PossibleHeavy contamination from clutch wear
- PossibleFilter changed without resetting the monitor
- RareFaulty main valve body (Allison serial range)
- Repair
- Easy · Often possible to do yourself.Typical cost: €60 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.