no 02 but no CEL

[azzkikr]

I dont have an O2 sensor in my car... or any exhaust for that matter. I am not getting any check engine light or error codes. Is the M30 supposed to throw an error if the O2 is not doing anything. It seems wierd that it wouldnt even care if the sensor is not hooked up at all. Anyone know anything about this?

[azzkikr]

Bumb for a response.... anyone want to unplug thier 02 sensor and see if they get a check engine light. 2 seconds is all it takes. Thanks

[arsevader]

I dont have an O2 sensor in my car... or any exhaust for that matter. I am not getting any check engine light or error codes. Is the M30 supposed to throw an error if the O2 is not doing anything. It seems wierd that it wouldnt even care if the sensor is not hooked up at all. Anyone know anything about this?

Have you actually run the car? The ECU ignores the O2 Sensor upon warm up so you won't get a CEL right away.

[azzkikr]

I have not actually driven it but I ran it for an hour letting it warm up and run at full temp. I ran it 30 minutes when I first re-built the engine then I changed the oil and the coolant. Then it ran for an hour and I took care of a couple of wiring issues that I found but I never got a CEL. I did put the car in gear while it was up in the air. I wanted to test that the driveshaft would work well.
I do have a problem with the coolant temp gauge. It doesnt register anything because I need to put in the E30 sending unit. The ECU should still get signal though because it is the same sending unit with the same ECU so the voltage/ohms will match. Maybe that is the problem though. Maybe its not telling the ECU the engine is warm and thus it assumes the O2 sensor is cold.

I will try swaping out the temp sending unit and running the car longer. I will let you know what I find. Thanks for the response.

[arsevader]

The ECU should still get signal though because it is the same sending unit with the same ECU so the voltage/ohms will match. Maybe that is the problem though. Maybe its not telling the ECU the engine is warm and thus it assumes the O2 sensor is cold.

I don't think that's how it works. The ECU would actually get its engine temp signal from the 2 prong temp sensor rather than the 1 prong gauge sensor.

Have you checked the obvious things like the light is actually working? Can you trigger a CEL for somethign else? Can you read codes out of the CEL even though it looks like nothing was triggered?

[rs4pro3]

do you actualy have the wire from the ecu harness, wired to the check engine light in the cluster?

[MrK]

I ran my m20 without an o2 sensor for a month (idiots who were repairing my exhuast forgot to plug it back in), and it never gave me a CEL, if that helps.

[arsevader]

I ran my m20 without an o2 sensor for a month (idiots who were repairing my exhuast forgot to plug it back in), and it never gave me a CEL, if that helps.

Interesting.

I failed an emission test in December becasue the morons at the testing place knocked the sensor harness loose and ignored the bright light glaring at them on the dash.

I of course went back and made a big stink about it and passed with flying colours.

[azzkikr]

Just to clarify a little. I had the CEL come on the first time I ran the engine. I forgot to hook up the mass air sensor. Anyway I fixed that right away . The second time I ran the engine, about an hour, I expected to see the CEL come on but it did not. I expected it to come on because I didnt have the O2 sensor hooked up. I was just surprised that it never came on and I was worried that other things might be wrong that are not triggering a CEL.

[azzkikr]

I don't think that's how it works. The ECU would actually get its engine temp signal from the 2 prong temp sensor rather than the 1 prong gauge sensor.

Yeah... I was just grabbing at whatever I could saying that maybe the ECU was assuming the 02 sensor was cold because the engine guage was saying it was cold. I said the ECU and the temp sending unit are the same so the ECU would be getting the correct signal for temp anyway. I was more just trying to get some ideas flowing and some discussion on the topic going. Thanks for the response though... I just didnt want you to think I was really that dumb :-)