Excerpt:
"Now for some theory on Computer Inputs and
Outputs. This is really simple once you understand
a few basic rules. Kinda like life, when you start to understand
a few simple things, it starts to work for you, but we won’t
go there...
Computer
Rule
#1:
Computers are dumb. They can only do what their programers
have told them to do. (They had you bluffed to think they were smarter
than they are?) And what they do is this simple: Input
... logic ... output.
Computers get input from their sensors. They look up in their
logic tables what they are supposed to do for this condition.
They they actuate something, they do something, like turn
on an injector for a set time or tell you what trouble code
they have stored. All computer operation is this simple. And
diagnosing a computer problem is finding out where they went
wrong. Was it a bad input sensor that caused the whole chain
of events to go haywire?. Was it a logic problem, like maybe
the computer memory needs to be updated, or the whole insides
of the computer is fried. (It's hard to put that smoke back
in once it gets out!) Or is there a problem with an output,
like a solenoid is stuck and can't move even when the computer
tells it to. That's all there is to it.
It only gets complicated when you don't understand all the
pieces to the puzzle. Maybe there's a sensor you don't know
how to measure, then how can you figure out the problem? Or
maybe there are a chain of computers in a network talking
to each other, and you don't know a problem with a sensor
for the antilock brake module will cause the engine computer
to not complete a drive cycle. If you don't know enough about
it, it gets hard. But if you know, it's simple.
Computer rule #2:
Computers depend on the engine doing it's job, being in good
shape. The rest of the engine must be good. (They are
truly codependent; ask your wife if you don't know what that
means...) The mechanical engine must have good compression
and develop good vacuum. Ignition timing must be adjusted
properly, the timing belt can't be installed one tooth off.
Fuel pressure must be correct, the fuel filter must flow enough
gas, the exhaust system must not be plugged up or leaking
near an oxygen sensor (you'd be surprised the kind of problems
a loose oxygen sensor can cause), the intake ..."
The article contains these sections:
- Computer Rule #1
- Computer Rule #2
- Computer Rule #3
- Basic Needs of an Engine
- Input Sensors
- RPM
- Load (MAP, MAF,VAF, KV)
- Throttle Position or Throttle Angle (TP, TPS or TA)
- Coolant or Air Temperature (ECT or IAT)
- Oxygen Sensor (O2 or O2S but HO2 or HO2S if it has an internal heater.)
- Fuel Trim
- Knock Sensor (KS)
- Outputs
- Final Computer Theory
