2002 stock ECU - what happens when ...
 

What inputs does the stock ECU pay attention to when the ignition key is simply turned to the "running" position. Not the accessory and without hitting the starter - just the "on" position?

For starters I suspect:

IAT sensor - is it in range
CLT sensor - is it in range
MAF?
EGR?
Idle ctrl vlv?
anti theft?

I suspect it does not check for connections (or input values) to(from):

O2 sensor
coils
injectors
a/c
alt
f/p
air bags
body elecs
headlights

Thoughts?

the ecu checks it all but ignores it if the rpm is less than a "running" threshold.

actually it doesn't check:
coils
injectors
air bags
most body elecs
headlights
to any degree that matters.

but maybe if you had a point why this matters?

When MS is installed I do not want to have any problem if the stock ECU is queried via the underdash diag port. I would want the stock ECU to say hello, all is well -

I would think other MS users would like the same thing ...

Now, what does the stock ECU look at before it would say all is well - if it never progressed past the key to "on" state?

IAT & other sensores are simply resistors as far as the ECU is concerned ...

If you are saying you want the car to pass OBDII inspection, it wont.

Get off your high horse - I am not some dreamy noob to ECUs and hotrodding.
Anything can be done and I will find the info I seek. If you have nothing but crap to add to this thread then don't add.

I guess you would have been one to say a Miata can't be turboed or get a V8.

Shame for a moderator.

The only thing you can do is give the stock ECU a bunch of false inputs if you're looking to for it to give an "ok" to the OBD plug and have an aftermarket ECU not running piggyback. Quite a bit of work to build a system of faux inputs to the ECU and have all the inputs in sync with what the ECU expects...you'd be building a computer to control a computer. Honestly, the switch between a standalone and stock depends on how lazy you are. Keep the EGR tube and a cat in the exhaust and things get really simple. Keep the MAF and all you have to do is swap injectors (since it's a given that you'll be running larger than stock with any aftermarket ECU). So either swap the basic parts- ECU, injectors, MAF and wire the WG open or just register the car outside of shitty metro-Atlanta

Wow, that's harsh...

I'm not sure I'm following this right.
If you're installing MS even in parallel, you just cut the wires which need to be cut (injectors/coils) and leave the others, everything works fine.

But there are write ups here that take the Mazda ecu out altogether with the MS standalone.

Either way, as soon as you turbo or tamper with the MAT/CLT/o2 signal, the vehicle will not pass the OBD2 tests required in inspections (well that's how I understand it to happen in the US).

What exactly are you trying to achieve?

Phew... do I smell the banhammer around...?

http://i41.tinypic.com/23hlked.jpg

Hey here's a thread that you might find useful!

https://www.miataturbo.net/showthrea...ighlight=obdii

Your questions are vague and non-technical. What do you expect for an answer? "the diagnostics port" doesn't just say "hey, lets have a beer!"

get an OBDII code reader.
You can see exactly what the diagnostic port is doing when you put the key in any position (I can offer a suggestion where to put it if you're interested).



Again, if you tell us what you want the diagnostic port to return and for what reason, maybe we can offer more than what you think is shameful.

Believe it or not, I'm not just a moderator, I've got some amount of experience with the 2001 miata and diagnostics port and parallel engine management installations. The short answer, as I've said, is that your OBDII diagnostics will not be "all is well".

If you just want to log data at the tragically slow polling rate of OBDII, you can still do that. But the MS will do it better.

I APOLOGIZE -

After getting a warning I reread the threads to prove to myself that y8s had been out of line.

I realized that HE WAS NOT. I guess I am getting crusty as I age.

I was trying not to directly mention emissions checking in my original post and since it would be illegal to spoof the authorities I will cease this pursuit.

I do appreciate the rich assembly of knowledge on this board and thank you for your comments.

moderators are never out of line.

You Sir are out of line.

sure it's illegal but that doesn't mean you can't physically try.

it's just really hard and kinda pointless and not really any more work to just swap out ECUs and injectors for inspections. which is also illegal. in most places with emissions inspections, driving the car with ANY chagnes to the engine management system is illegal. we're all crooks!

I would think the easiest way to keep it happy is to not steal its sensors.

The MS can use standard GM sensors which can be added to the your motor allowing the MS to control the injectors and the ignition (the outputs for the stock ecu for injectors isn't monitored directly)

This setup would not eliminate the CEL from lighting when the stock ecu see's an out of range signal input for the O2 sensors or lack of change in a closed loop mode but it would be a step closer to your goal.

I am not supporting the idea of tampering with emissions equipment on a road going vehicle, but the more trying to answer your question on how not to disrupt its normal operation in the event of a megasquirt being present for some given reason.

I've made ODB-II legal MS installs.

share the inputs, and cut some of the outputs from the stock ecu and have the MS do it.

:bowrofl: :bowrofl: :bowrofl: