O2 sensor output

[Jeremy Fleming]

On 12-Sep-97, alex nicu wrote:
>Anyone thinking on using a microcontroller to make that O2 sensor output 
>to be readable ? 
>If you have any detailed info of the output , I can spend some time to 
>implement an correction map , if this is posible .
>Alex


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Alex,

Actually, I am, sort of.  I've been kicking around the idea of
building a diagnostic code checker for my '86 RX-7 using a
PIC.  It won't really be looking at the O2 sensor, though, as
the diagnostic connector has three open collector lines off of
the ECU- two that show the tens and ones of the code, and one
that blinks to show (I'm guessing) the status of the O2 sensor.
The factory manual says that you should see x blinks in y amount
of time.  If it is, say, on when the O2 sensor is high, and off
when it is low, x number of blinks per unit of time means that it is crossing
the stoich point x times.

Anyway, seems to me to be pretty straightforward to count the
HI/LOW transitions per unit time and give a number (not AFR, but
a blink/time value) that you could compare to factory specs.

If you're wondering why I want to fool with such a stone axe application- the
dealer wants many hundreds of dollars for a
genuine mazda code checker, and I'm just getting into microcontrollers.
Seems like a no brainer, but these kinds of things usually prove
my absence of brainpower.

Jeremy

jeremy at dtc.net