My check engine light came on after I replaced my EHA with a used one. My previous EHA was bad and would leak. The one I replaced it with does not leak. I bought 2 used and no matter what one I put on I get the CODE 17. Someone suggested that it might be the O2 sensor itself, so I went out and bought another and put it on seeing how mine was last changed 41k miles ago, but I still get the CODE 17 even with the new O2 sesor. Any suggestions on how to remedy this?

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1990 190E 3.0L

Most likely the fuel mixture need adjustment now.

Either too rich or lean & the O2 sensor doesn't have control of the mixture.

Do you have a DMM with duty cycle ability?

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I don't have a DDM, what is it and how do I adjust the mixture?

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1990 190E 3.0L

I bought a multimeter today and this is what I found at the O2 sensor ecu wires:

green wire: 0.4v engine off
both white wires: -0.4v engine off

green wire: 0.4v engine on
both white wires: 11.7v engine on.

These are the wires under the passenger side mat connected to the computer of the car.

I tried testing the wires to the actual O2 sensor and didn't get any reading both with engine on and off.

This is my first time ever using a multimeter. Are my readings correct? If not how do I fix them? These problems only started happening after replacing the EHA with a used one.

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1990 190E 3.0L

On my 1992 500E the ECU sends .45 volts as a simulation of the O2 sensor output until it warms up. There after it cycles between a high value and a low value somewhere between 0 and 1 volt in order to control the air fuel ratio between say 12 to 17 depending upon engine operating conditions.

Ok, so I believe the Code 17 has been cleared....but I'm not exactly sure which solution clered th code. Here is what I did:

1) I originally bought a new O2 sensor that I spliced into the fitments of my oe so I took the 2 heater wires (white) and I interchanged them with one another (not sure if that made any difference since they are both the same)

2) I slightly adjusted the fuel mixture tower. There was I small steel ball in the top opening and on the side of the tower was a small hole which allowed me to stick a small hex key in and lift the ball out. The whole procedure took less than a minute.

3) I boutght a used EGR valve and replaced mine. This was a pain since my valve was pretty much fused to the damn manifold. 20+ years of heat! Once I got it off, I cleaned the area around it, scrubbed the gasket with a wire brush, sprayed the thread holes with silicone and then I decided to coat the gasket, the bolts and nuts, all the threads of the holes, and the bottom rim of the EGR valve with dielectric/anit-seize grease (highly recommended if someone has to replace their EGR or anything on the manifold)

4) I swapped out one of the EHA valves with the other one I bought.

Drove the car all day today and no CEL and it usually comes on in 30 minutes after driving, so I think I'm set.

Cheers!

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1990 190E 3.0L