P088A: Transmission Fluid Filter Deteriorated

What does P088A mean?

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.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

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

Common causes

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

Likelihood is a general estimate across vehicles; your make and model may differ.