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      12-20-2011, 05:15 PM   #27

Drives: BMW 335i
Join Date: Oct 2010
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2008 BMW  [3.12]
Originally Posted by cn555ic View Post
Tested the older unit out and it doesnt seem to work It shows flow of 78-79 but the Procede unit keeps throwing a overflow code and goes into a valet mode which makes the meth system not work...I guess I need the newer version one! SUcks bigtime
You can use 2 resistors ($1 total) and make a voltage divider. If this sensor outputs 0-5v and Procede needs 0-3.3v range (I remember reading something like this on the forum earlier this year), just make a voltage divider and you are good to go:

In order to choose the resistors, you first need to measure the current between the sensor and the Procede using a multimeter. Then using the Ohm law ( I = U / R ==> R = U / I = 5v / measured current) you can find out the total resistance needed (R1 + R2) in order for the current to remain somewhat the same. And then using the voltage divider equation (3.3v = (R2 / (R1 + R2)) * 5v) you can find out R1 and R2. And that's it. You can also use a single potentiometer instead of 2 fixed resistors, so you can better adjust the sensor to the Procede.

Last edited by tscdennab; 12-20-2011 at 05:24 PM.