I'm working on my 92 240 which is new to me so I'm going over a few maintenance items. And at this point, I could use some help. The check engine light came on while I was bringing it home.
A check of the codes tells me the Oxygen Sensor is missing or faulty. While follow the lead of the Oxygen sensor the plug came apart as soon as I touched it. The male end wasn't fully seated.
Looking at the female side of the plug there is a metal snap and I'm not familiar with how they work. Do I just push the male side in and it snaps together, or do I need to pull the metal snap out so I can insert the male end?

Thanks in advance.

 

The single wire is the output from the O2 sensor. That type of sensor you can read the output with a volt-ohmmeter. Voltage output when warmed up (and a reasonably running engine/ no miss fires/ no air leaks/ etc) would be seen as dc voltage varying rapidly between .2 and .8 volts.
Measure with the output wire disconnected. The other 2 wire connector is for the heater element in the O2 sensor. The heater is there to warm the sensor up quicker when engine is first started so it starts working quicker (needs to be a certain temp to be accurate)
Do you still have a cat installed? (or it's not been hollowed out?) If so it would be best to have a working O2 sensor. But If money is tight - you can run your car with the O2 sensor disconnected. It really can't change the mixture very much. If you want to see if the O2 sensor responds to rich and lean mixtures - you can send rich or lean signals easily. With the sensor disconnected, warmed up and reading your .2-.8 volts - ground the green wire to the ground strap or engine and watch the voltage change. Then touch the spade terminal of the the green wire with one hand and touch the positive battery terminal with your other hand - that will send a small voltage to the control unit and you should see the measured voltage change also.

 

hoonk, sorry for the delay in replying. I was able to get the male plug seated even though I pulled on the metal clip instead of pushing, it seams the connection is fine. Anyway, the check engine light went out and then came back on the next day, and I believe it has to do with the idle control vale. So, I'll be removing that and cleaning it in the next week or so. At the same time, I want to replace the flame trap and short Z shaped hose plus I want to clean the throttle body. I checked the little nipple that screws into the manifold and that was clear so I'm hoping the larger rubber hoses will be good to or do you think I should just replace them?

To answer your questions, it looks like the previous owner installed a new O2 sensor and the cat is still installed. I don't have reason to suspect it was hollowed out.

 

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