Introduction:

Next, let's look at some Computer Examples, to see how the inputs would combine to tell the computer what the condition is, and we can see how they would affect the outputs. Let's make up a sample car to do this, I call it the Theory Car (it only comes in "on-line blue"). It has a normal sequential fuel injected four cylinder engine, similar to the ASE Composite Vehicle #1, if you have heard of that. Notice that there are two possible ways of measuring load. Most Theory Cars have a MAP sensor. But some have been ordered with the MAF sensor option. That way I can ask you questions related to a MAF sensor system. We have these kinds of input sensors with these kinds of values:

RPM: a magnetic pickup but the scan tool just shows the RPM
LOAD: the MAP sensor puts out an analog voltage. Idle at 18"Hg will give us 1.0 v, and wide open throttle with 0"Hg will put out 4.5 v. The MAF sensor option is also an analog voltage. Idle will be about 0.5 v and wide open throttle will be about 4.5 v
TPS: an analog potentiometer that gives us a variable voltage, with 1.0 v at closed throttle idle, and 4.5 v at wide open throttle.
ECT: Engine coolant temperature sensor that is a negative coefficient thermister which gives 3.5 v at 32 degrees F and 0.5 v at 195 degrees F.
O2: Normal zirconium oxygen sensor where values below 0.45 v are leaner than 14.7:1 and values higher than 0.45 v are air-fuel ratios richer than 14.7:1.
LFTRIM: Given in %, where +% is adding time to the injector pulse width to richen the mixture, and -% is subtracting time from the injector pulse width. Normal values can be ..."

The article contains these sections:

1. Introduction
2. Example #1
3. Example #2
4. Example #3
5. Example #4
6. Example #5