I did tap it...

Right at the HO2S harness.

I seperated the harness, slipped the signal wire into the socket, and re-connected the harness. I didn't actually split the and solder the wire, as this was only a test.
I'm hoping that this is only a result of a bad connection. My local electronics shop is closed till Monday.

The CEL was easily reset - just disconnected the battery for 2 min...

 

I see, then I don't understand why it threw CEL.

 

me either... that's why I'm confused...

 

<div class='quotetop'>QUOTE (Zenador)</div><div class='quotemain'>Ok, I built one, and ran a test on my car (04 I4)

Works!!!!!

BUT - The car throws a CEL with it connected.

Anyone have any ideas?</div>

What resistors did you put there?
I built too, but i've got all LEDs on or none of them.

 

I didn't use resisters, I put Potentiometers on it, and set the resistance on them.

If you only connect the power supply lines, and not the sensor line, all lights will be on. If you then connect the sensor line to a voltage over 1.0 volt, all the lights will go off.

I had some almost dead watch batteries (0.3 V) which I grounded to the test 12V power, and touched the positive side to the sensor line - only 3 LEDs came on.

 

<div class='quotetop'>QUOTE (Zenandor)</div><div class='quotemain'>I seperated the harness, slipped the signal wire into the socket, and re-connected the harness. I didn't actually split the and solder the wire, as this was only a test.</div>

According to what you say here, you disconnected the 02 from the harness. That would be what threw your CEL.

 

Disconnected wiht the engine off. wouldn't make a difference. Once the probe was in, the harness was put back together, then the car was started.

I disconnected and reconnected it before was attached, to make sure the car wouldn't throw a cell....

The only thing I can think of is the digital meter is causing a voltage drop before the signal gets to the ECM... I have to check that.

 

I was posting that and then I re-read your earlier post. If everything is back the way it is I'd have to say that is the problem.

I know you want to keep this cheap, but what about adding in the wideband 02 sensor as a third bung and just not touching the other 02's??

 

just now found this DIY... good one. once i get to germany i'll have to find their equivalent of a radio shack... this'd be cool to have

 

That's so awesome... But I'm not very good at that stuff... I'll probably have to get someone to help me, or make one for me when I have money.