Here are some of the transfer functions between the various sensors and the 68HC11's ADC.  The MPU's ADC is mux'd to one of eight inputs (AN0 through AN7). All the inputs to the ECU have some high frequency by-passing, some have more filtering in a couple of the encapsulated modules (HY1 & HY2).  These functions represent their DC characteristics.
 
 

AN0	This input is multiplexed through an external CMOS switch.  All of the inputs to this switch are not loaded so they have no meaning to us.
AN1	This is another NC.  It goes to pin-9 of the main input connector though a small resistor network.  Hard to tell exactly what it was intended for.
AN2	MAT input from HY1.  The resistor network is pulled up to a 4.3 volt supply so the voltage to the ADC is offset.
AN3	Coolant sensor input.  It is conditioned in the same manner as the MAT input, also through HY1.
AN4	This is the O2 Sensor input.  Its output  goes through a small resistor network then multiplied in HY2 by 3.072.  The resistor network also adds in a small offset voltage.
AN5	This input is tied to the TPS.  There is an 1:1 relationship between the TPS output and ADC input voltage.
AN6	The Battery voltage is directed to this input.  The HY1 module divides the input voltage by 3.2103 before directing it the ADC.
AN7	This input is tied to the MAP sensor.  There is a 1:1 relationship between the MAP output and the ADC input voltage.