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another egr thread...how to fool the ecu

4766 Views 2 Replies 2 Participants Last post by  patallen
My EGR valve diaphragm is leaking so i got a "insufisient flow" code.

I was wondering if anyone did try to fool the air flow meter output so the ecu think there is a flow leak when the egr is activated...i think it could be done easely, just a relay connected to the egr solenoid and a trimed resistor value that would be put inline of the afm flow signal with the relay (on the NC connections of the relay)...
i am hell frustrated to see the CEL and to pay 199$ for a %?"/$% egr valve assy'.

this might be just a temporary solution as i am looking for a good used valve assy's.

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Someone tried a trick where they twisted the MAF sensor. It didn't work for very long. I think a used assembly is the best bet. You could call a local junkyard and they will search other yards for you.
yeah, i know that semi trick...with due respect to the guy who try it, logicaly it couldnt work, the ECU needs to see a flow loss when the EGR is activated only, not all the time. As an electronic engineer for the automotive market, i would do it that way, and that would be the simplest EGR strategy...

assuming rpm is within a range, or the engine is coasting:
1-record actual air flow/rpm
2-activate EGR solenoid
3-measure new air flow/rpm

Calculated Air flow/rpm loss must be less than xx% to xx%, if not then see margin, and set appropriate code (inssufisient egr flow or too large egr air flow)

If the AFM is an analog outputs, 0-5v type (not 5-0v) , then my solution might work and will be very easy.

-1 automotive relay, energized in place of the EGR solenoid
-1 trimed resistor added in line to the analog output of the AFM, resistor ends shorted with the relay contact 30 and 87A (will try to measure impedance input of the ecm circuit then calculate a 5% loss as a start point).

During normal operation, AFM signal flows thru relay contact 30 and 87A, thus unaltered. When EGR is asked for, the relay gets energized, openeing the normal afm flow, but passes thru the trimed resistor only, thus reducing AFM voltage output, simulating a flow loss...

Disclaimer, i am not assuming anything at all, or that it will work. If EGR is activated thru PWM signal then it wont work, and if egr flow loss is not linear then it wont work either since the resistor/flow loss will be linear in regards to actual flow...

I will simply try it for sure and will let you know.

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