ECM Program logic?
Thread Starter
Racer
Joined: Sep 2002
Posts: 317
Likes: 1
From: Maple Valley WA
ECM Program logic?
I've looked (albeit somewhat cursorily,) for a description of the program logic contained in the ECM (for my '95.) I can't find it anywhere.
What I'd really like to know is this: From the moment the key goes on, what does the computer do? Starts out in open loop mode? (- what does this mean?) When does it start polling sensors? in what order? When does it enter closed loop mode? What is the logic of the main loop? etc.
Any help?
Thanks,
Jay
What I'd really like to know is this: From the moment the key goes on, what does the computer do? Starts out in open loop mode? (- what does this mean?) When does it start polling sensors? in what order? When does it enter closed loop mode? What is the logic of the main loop? etc.
Any help?
Thanks,
Jay
Le Mans Master
Joined: Oct 2000
Posts: 6,362
Likes: 30
From: Oak Harbor WA
Re: ECM Program logic? (JayH)
I've looked (albeit somewhat cursorily,) for a description of the program logic contained in the ECM (for my '95.) I can't find it anywhere.
What I'd really like to know is this: From the moment the key goes on, what does the computer do? Starts out in open loop mode? (- what does this mean?) When does it start polling sensors? in what order? When does it enter closed loop mode? What is the logic of the main loop? etc.
Any help?
Thanks,
Jay
What I'd really like to know is this: From the moment the key goes on, what does the computer do? Starts out in open loop mode? (- what does this mean?) When does it start polling sensors? in what order? When does it enter closed loop mode? What is the logic of the main loop? etc.
Any help?
Thanks,
Jay
Think of it this way: Open loop means that the ECM and Injectors operate independently. Closed loop means the ECM, O2 and Injectors all work together.
For the best understanding, go to Barnes and Noble and buy a book called "How to Tune and Modify Chevrolet Fuel Injection" by Watson.
Thread Starter
Racer
Joined: Sep 2002
Posts: 317
Likes: 1
From: Maple Valley WA
Re: ECM Program logic? (Goody)
Yes it starts out in Open loop until certain conditions are met. O2 sensor don't start working till they reach around 600*F, so the ECM using stored fuel mappings based on set values until the Closed loop operations start. Then it can adjust the fuel/air IAW the feedback from the O2 Sensor.
Think of it this way: Open loop means that the ECM and Injectors operate independently. Closed loop means the ECM, O2 and Injectors all work together.
For the best understanding, go to Barnes and Noble and buy a book called "How to Tune and Modify Chevrolet Fuel Injection" by Watson.
Think of it this way: Open loop means that the ECM and Injectors operate independently. Closed loop means the ECM, O2 and Injectors all work together.
For the best understanding, go to Barnes and Noble and buy a book called "How to Tune and Modify Chevrolet Fuel Injection" by Watson.
OK, I'll look for the book. Hopefully that'll have the specifics I'm looking for. I really don't want to get into a full disassembly of the program code (heck, I don't even know if the ECM will output that to me or not through its interface.)
Jay
