I'm looking at an N327 ECU, and I'm hoping someone can help me out. I assume the ECU interprets 5V referenced sensors by looking at the voltage at a voltage divider, where one half the divider is the sensor, and the other half is a resistor somewhere in the ECU. I'd like to know what that other half is so I can predict what voltage to expect at a given sensor resistance.

I can come close with certain sensors, like the water thermo sensor, where based on these S5 values:



I come up with about 2.3k that should be between the water thermo sensor input pin and ground somewhere in the ECU. I'd like to confirm that, especially because those values came from the S5 FSM, not the S4 FSM, and not all sensors have the data available that the water thermo sensor has. In tracing the route the water thermo sensor takes through the ECU, it comes in through pin 2I, passes a bypass capacitor, and then goes into a pin of this device:



What is that thing? Some of the pins go through resistors, others diodes, and some go to a digital IC connected to the microprocessor. Could that be a relay? I was originally thinking a filter, but a specialty relay makes sense too.

So I have two questions:
1) Is my assumption about how the ECU samples sensors correct?
2) What is that HC128 doohickey?

My Google searches only came up with RX-7 ECU pages (including one on this forum) that don't know what it is either. Thank you much!

 

I'm just going to log ECU voltages for simulated sensors (I'm trying to make some lookup tables for my display project) and be done with it. My guess is the 2.3k will turn out to be correct, but if not, the LUT will take care of it anyway.