Re: 02 Voltage Calculation

[Ludis Langens <ludis@cruzers.com>]

Berg Family wrote:
> 
> Does anyone know what the formula is for calculating the O2 voltage coming
> from the diagnostic data on a '730 $8D data stream ?

First you need to convert the O2 byte into the voltage seen by the ADC
chip.  This chip has a negative reference of ground, and a positive
reference hooked to the "5 volt" VCC supply.  Every ECM I've checked
seems to run VCC a bit high - something like 5.1 volts.  There is a
possibility that GM runs VCC at 5.12 volts so that the ADC values are in
0.02 volt increments.  The ADC output is a value from 0 to 255.  You'll
have to figure out how it rounds.

Once you know the ADC input voltage, divide by 4.5 to get the O2 sensor voltage.

-- 
Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/


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