inferred mileage
In 1981 Ford started installing an "inferred mileage system" on trucks with a 302 and the AOT (AOD) automatic transmissions to be sold in California. The 1986 EVTM says "After a specified number of miles the Inferred Mileage Sensor (IMS) changes a signal voltage to the ECA, this changes the internal calibration, compensating for the engine break-in period (5.8L only)."
Here's the schematic from the 1986 EVTM:
Here's the schematic from the 1986 EVTM:
Here are the part numbers: