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Old 07-05-2009, 03:57 PM   #1 (permalink)
mhopeng
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Arrow What does an injector signal look like?

I'm connecting MPGuino to a 1990 Toyota 4Runner. My ECM connector pinout is:

E01 No10 STA Vf NSW
E02 No20 IGt E1 n/c

where the pins are described as:
No10: "Injector"
No20: "Injector"
E01: "Engine Ground"
E02: "Engine Ground"

I borrowed an oscilloscope to look at the No10 and E01 signals. The No10 signal was a high pulse (> 12 V), while the E01 signal was a small negative pulse, more like 0.5 V. Both pulse frequencies correspond to changing engine rpm (pressing the gas while sitting in the driveway).

The shorthand directions for finding the Injector signal call for finding the signal which is *not* 12 V, so I connected the E01 signal to the MPGuino, and it doesn't work (no injector pulses are recorded). So the obvious thing to do is try the other pin, but I thought I would check here first, because its a pretty high voltage.

So, in general, what does the MPGuino expect the injector signal to look like? What is the safe input voltage to an input pin on the MPGuino board? The "Injector" signal seems to be a pretty high voltage spike, higher than the ATmega datasheet allows (maybe this what the zener diodes at the input pins are for?).

Given the choice between the two signals in the picture, which one is most likely the correct INJ signal?

Thanks!!

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