O2 Sensor Wire - PeachParts Mercedes-Benz Forum

redsl · #1 08-31-2008, 03:13 PM

I opened up what I belive is the Lamba Unit, under the foot area in the fire wall. It has a large connector with about 9 pins. I am trying to find out which wire goes to the O2 sensor. Someone cut it off completely and I have no clue. Engine running very rich can smell gasoline. Please HELP!!!

deanyel · #2 08-31-2008, 04:35 PM

I'm guessing you have a red SL - but it's hard to guess the year and model. If you provided the year and model someone might be able to look up the wiring diagram and tell what color wires you're looking for.

timm9 · #3 08-31-2008, 05:35 PM

I'm very curious to see if indeed someone cut the wire or if it is actually housed in the large wiring loom going into the CPU. On my 82 380SL you can't see the wire either. Once it leaves the sensor, it is routed through the frame and not easily traced. If someone knows for certain I would love to hear about it.

redsl · #4 09-01-2008, 08:39 AM

So frustrated that I forgot to put the year 1981 and the model 380SL. In the mean time I found one black wire under the hood that was shielded but when I tried to do a continuity test on the main plug to the Lambda control and that wire, I did not get any. So I guess that was not the wire. There are no more (loose wires) that I can see.

deanyel · #5 09-01-2008, 10:47 AM

I think you should buy the 107 service CD from MB at 800-222-0100. It will have a complete wiring diagram so you'll be able to figure out what has been tampered with. And it seems to me the 107 version is quite cheap.

Nascar Fan · #6 09-01-2008, 12:16 PM

redsl · #7 09-03-2008, 05:08 PM

Quote:

Originally Posted by Nascar Fan

Attachment 58697

Thanks for the diagram. Unfortunately the large pin does not have any numbers asscociated with it so its hard to determine the pin location. There are many holes that do not have contacts in them. I cut open the large loom and found one black wire that seems to have a coaxial covering on it, but don't know for sure if thats the one. You can not see it wafter it goes up into the dash area. If someone can give me the location it comes out maybe I can cut into the wire and extend it to the O2 sensor.I guess I will keep trying thanks for your help. If there is anything else you can telll me about this it would be appreciated. thanks

pwogaman · #8 09-21-2008, 09:24 PM

What color are the wires that were cut? I might be able to help you with that additional information.

ctaylor738 · #9 09-23-2008, 08:34 AM

You can get oriented on the connector by finding pin 16 (brown, ground), and pin 8 (+12V ignition on, red/blue).

Other pin-outs:

15 frequency valve & diagnostic socket brown/green
6 idle speed control & throttle switch, blue
5 ground for throttle switch, brown
7 throttle switch & idle speed control, green & green/wht
4 & 2 o2 sensor, color ?

You should also be able to get the car running acceptably without a sensor by grounding the wire that runs to the temperature switch on the oil filter housing. That should throw the duty cycle to 60/40, and you can adjust the mixture to get it more or less right. If you have a working sensor, you should adjust the mixture to get something like .5 volts between the sensor and ground

450slcguy · #10 09-23-2008, 12:54 PM

Quote:

Originally Posted by redsl

Thanks for the diagram. Unfortunately the large pin does not have any numbers asscociated with it so its hard to determine the pin location. There are many holes that do not have contacts in them. I cut open the large loom and found one black wire that seems to have a coaxial covering on it, but don't know for sure if thats the one. You can not see it wafter it goes up into the dash area. If someone can give me the location it comes out maybe I can cut into the wire and extend it to the O2 sensor.I guess I will keep trying thanks for your help. If there is anything else you can telll me about this it would be appreciated. thanks

It does have terminal numbers associated with it. The termnal numbers are on the board side of the connector. Pull the board and look on the back side of the connector. Terminal 2 is O2 voltage, terminal 4 green ground.

redsl · #11 09-23-2008, 02:07 PM

Quote:

Originally Posted by 450slcguy

It does have terminal numbers associated with it. The termnal numbers are on the board side of the connector. Pull the board and look on the back side of the connector. Terminal 2 is O2 voltage, terminal 4 green ground.

How does the board release from the metal boxed housing. I do not want to damage this board as you can imagine, $$$$. Is there an easy and safe way to get it out?

450slcguy · #12 09-23-2008, 07:03 PM

2 screw on the back of metal enclosure, slide out from front.

redsl · #13 09-24-2008, 03:19 PM

Quote:

Originally Posted by 450slcguy

2 screw on the back of metal enclosure, slide out from front.

I will try it on Saturday. Have to put in some more hours at work to pay for all the other parts I needed to purchase. Wife is not a happy camper about me and my car LOL.