kurtwz

I’m currently installing a set of long-tube headers and the bung for the rear o2 sensors on both sides are too far back for the existing o2 sensors to reach. What would you guys do in a situation like this? I consider my three options to: 1) Get an extension cable or replacement o2 sensor with a longer cable, 2) Cut the cable and splice in a longer cable, 3) Not use the rear o2 sensor at all.

1) Does anyone know of an extension cable or replacement sensor with a longer cable? I know they’re available for different makes, but after some searching online and calling of local parts store and a Mercedes dealer, it doesn’t look they’re available for Mercedes vehicles.

2) How do you guys feel about cutting the cable and splicing a longer one in? To me this makes me nervous, but it might work. I figure the worst I’d have to do is buy replacement sensors, which would be pretty costly, but of course I’d like to avoid it if possible.

3) What would happen if I’d just plug up the bung hole and remove those sensors all together?

Are there any other options I haven’t thought of or any advices you could offer?

TTMotorsports

Why not call the company that made them and ask WTF?

If you have to extend the harness do it before the plug going into the O2 sensor connector. Do not extend the wires on the O2 sensor harness!

shardul

iTrader: (1)

Make sure you upclip the wires and they should extend to the 2nd O2 bung

kurtwz

Hey Shardul. I tried that. No dice. I unclipped the connector and pulled as much slack out as possible and it's not even close. I'd have to get about another 2" from it to get there.

Yeah, I'm trying that now, but not making much progress . Why is it important to not extend the length of the o2 sensor harness? Thanks

sneakyneon

+1, o2 sensors are sold as a universial part that you can cut and add your pigtail too, do these not work right?
As for your problem I would not use the down strean 02 sensors, have a tuner turn off the odb light.wile As a side note there is a good 10 to 15 hp to be had from not using cats!

MarcusF

Because you don't want to cut the factory wiring harness. Cutting the wires on the O2 sensor is preferred. Based on experience with the Bosch universal O2 sensors, the sensor uses stainless steel wire and it's almost impossible to solder. Use crimp connectors. Bosch includes these with their universal Bosch O2 sensors, you can probably pick some crimp connectors up at Radio Shack. You may want to heat shrink them when you're done.

nick 55

Did your headers come with any work notes at all? I would have to agree with TTMotorsports, but I feel this needs to be mentioned also. If you remove the primary catalytic convertors, and reinstall both front and rear oxygen sensors, you will get a check engine light for "catalyst insufficient effect" unless you have had a tune to turn off the rear O2 sensor monitoring. Essentially, you need a tune regardless unless you weld in some high flow catalysts, and they need to be pretty good ones($400 jobs probably won't cut it), so you don't get those codes. The rear oxygen sensors on out cars are used to monitor catalyst efficiency for emissions compliance. As far as extending the wiring to fit the headers, do not extend the leads on the sensors, as like marcusf said, the leads are very difficult to solder, and you will have a 2% success rate if you try that. Extend the copper wiring of the body harness, using quality wire of the proper gauge and solder connectors from MB if possible(PN# 0015469941). They are kind of expensive at a few bucks each(you will need 16), but we love our cars, and we don't put cheap, crappy parts on them anyways.

Nick

OXOJE55

Please let me know Dyno comp reply

kurtwz

So I found out that even though many makes come with a “rear o2 sensor delete” option after modification, to remove the rear o2 sensor would cause damage if driven indefinitely. So that is not an option.

With that in mind on Friday I was all set to attempt a splice to get some added length in there. I got all my bits and pieces together for that and I decided to take one last stab at getting as much length out of the stock cord as possible. When I looked at it that time I noticed that the cable goes through a tunnel before it reaches the bung. After I removed the plug from its clip and took the cable out of that tunnel and streeeeched it for all it’s worth (without putting the wires at risk of being disconnected), I was able to just barely get it to the hole. So I avoided needing to do anything else with it! That’s like the ideal outcome.

Anyway, thanks for the help, guys. I really appreciate the support and expertise even though I didn't have to use the splicing this time. Now if I ever absolutely need to extend that cable, I know how it can be done!