jimbo69

I have a couple of questions E3 ECM

What outputs do you get from the ~CRANK analog signal, does it tell crank position, if not why is it analog? I know that it tells the computer that you are cranking over the motor.

What is PSPS?

Why IS ~ACREQ signal analog?

Is PN park nutrual? Why is it analog? is this also used for the clutch on manual transmissions?

See pic for schematic

Ken73

PSPS = Power Steering Pressure Sensor. I believe it was used on V6 applications where power steering drag had more of an effect (Although the application may vary.)

~CRANK is grounded when you're cranking the motor over. Not quite sure what exactly it does for the ECM though. (Probably voltage correction for pulse width?)

~ACREQ is A/C request - tells the ECM when your compressor is kicked on, so it can add fuel if need be to keep the idle up.

PN is Park/Neutral, just as you suspected. Tells the ECM when it's in gear, basically.

jimbo69

Thanks,

Good don't need PSPS I only have 7 usable a/d lines and if crank just goes to ground then that is fine also, just use standard port for it. A/C compressor should be on/off also or I don't need to use it at all.

I'll have more questions later on... But am working on the schematic.

Morley

The crank is used (I believe) for crank "counts" as in the ref pulses from the dist when first cranking, it has to know how many pulses during cranking to get the added fuel for cranking (starting) in there.

The AC request should be tied (in the ECM) to the IAC and fan #2 relay. It adds steps to the IAC during idle with AC running to keep the engine alive (also engages/disengages compressor at different engine loads) and grounds the #2 fan relay to turn the fan on.

The_Raven

Crank, is positive signal, that if it's used has a fuse in the fuse box, not all C3 ECMs used it, most did however. It s tied to the ignition switch, and only goes active for the period that the engine is cranking (starter engaged)
I do not know it's purpose in refernce to the ECM, I can only speculate and think that it may be for a start retard, or cold start injector use, or something along those lines.

Morley

Cold start injector is independant of the ECM, it uses a thermo-time switch to activate it.

jimbo69

From looking at the code, it looks at the crank signal to start the injectors in a tbi system and initiates starting procedure. From there I believe it looks at the distributer signal to see if the engine is running and adjusts IAC. Only went through the code once so far. 150 pages of ROM takes a while. Seems to be some fluff in there also. The megasquirt code turns on the injectors full while cranking.

Something I haven't gotten to yet is the spark, is there a seperate controller that the ECM talks to or does it do the spark also. Looking at my manual it looks like the computer communicates with the spark system.

I printed out Megasqirts assembly code, it's a lot easier to follow at only 50 pages or so. But does not do spark.

Here's the IAC schematic. Page 1 and 2

jimbo69

Oops

I'm assuming that the IAC is pwm controlled or is just stepped.

jimbo69

Well I've been working on another project that makes money. But I have the interface for the display and IO expansion working. I'm going to play with the motor drivers next to see if they can drive the injectors ok, they are only rated at 2 amps 12v, may need to get some bigger drivers or have the computer fan cooled. But they do have inductance feedback cancellation built into the chips.

Hopefully this week I will be able to show some picks of the injectors spraying

TORC

I believe the crank signal is also used to activate the fuel pump relay until oil pressure can build up to close the oil pressure switch..... I think.

Grim Reaper

Sorry guys, but this post looks MUCH better on the DFI/ECM Board. Now you can get RBob to help too.

JPrevost

The cranking in most TBI applications have a seperate desired cranking afr vs temp. That's what the cranking input is used for .

jimbo69

Here's what I've been playing with utilizing the display, and suggestions would be helpful