I want to hook up my gauge tomorrow and I need to know what wire to tap into at the O2 sensor. I didn't even look at the sensor yet to see what is there. Where is it located compared to the waste gate? Must you go from under the car to acess it? I am also curious about the universal sensors. From what I have read on here this is my take on the different sensors if somebody could tell me if I am on the right track. The three wire sensors add a ground wire to be connected to the chassi instead of useing the exhaust as a ground. The 4 wire adds another wire for a heater that you must connect to?(a switched ignition wire) At what point does the 4 wire sensor benefit you?

Thanks

 

I just replaced my 3 wire O2 sensor with a 4 wire sensor and rehooked up my ARM1. First, the three wire system has two whites and one black. The ARM1 orange lead taps into the black. I thought the three wire system was not heated, but I now believe it was and the two white leads are the heater wires. Someone please confirm. The four wire universal O2 sensor I bought from Paragon has an extra brown lead, which should be taken to chassis ground or battery negative. Replacement of the O2 sensor is from below with an open ended wrench. Unplug your sensor on the top and pull it down from the bottom. You may have to encourage it around some heat shields. Splice your new sensor to the old cord. I dropped the new sensor down from the top near the oil cap behind a heat shield (straight shot down) If all you are doing is hooking up an A/F meter to your existing O2 sensor wire, it can all be done from the top. I pluged mine in about 6 inches from the connector behind the intake manifold. Good luck.

 

My question is, do you just splice the gauge wires to the old without breaking the connection from the old wiring to the sensor? I imagine so, so the computer doesn't lose its tiny mind. But does the sensor signal get futzed up by the fact it's sending to 2 destinations? Is there signal degradation?



Thaddeus

 

You can tap into the O2-sensor line inside the car at the DME. I've got a how-to page on my <a href="http://members.rennlist.com/951_racerx" target="_blank">951 RacerX website</a> on this procedure with details on which wire in the DME connector to tap into.

 

you can just tap right into the wire....my gauge came with "vampire" style clips that you clip down over the existing wire to make the connection. I think this way is acceptable, but a better (cleaner connection) way to do this would be to strip off a piece of the O2 wire insulation, and solder the A/F wiring to the O2 wire, then re-insulate. On mine I basically created a pig-tail connection to the O2 so I can change out the A/F if I later want to use a different one....I'll just unplug the current AF wire from the pigtail, and plug in the new one.

the other thought is to try to ground the A/F ground directly to the batt neg terminal....I know a few guys who have gotten weird af readings that were fixed after geting a more "pure" ground.

 

tazz:
a heated o2 sensor starts to work faster after you start your engine. this means that in theory the engine could switch to closed loop fuel control sooner. the extra ground lead for the sensor in a 4wire benifits you by providing a ground path which is less likely to vary in impedance than the exhaust plumbing.

thaddues:
connecting multiple loads to the weak output on a sensor CAN be a problem so your concern is legit, but in this case i'm pretty sure it's ok. I can't imagine that a reputable gauge manufacturer would assume that you are putting in a second o2 sensor just to run your lambda gauge and so they would set about to accomplish the not difficult task of making an input stage with very high impedance so that it can measure the voltage output of the sensor without loading it down and giving the ecu erronous data.
which means: you are right, just splice into the wire on it's way to the ecu... certainly don't break that connection.

txheg:
those "vampire" style connectors really suck... i've seen them weaken the wire they are attached to so that it breaks on its own later, i've seen them fall off.... i've seen them give intermittent connections.
just take the extra 5 minutes to do it right, especially on a sensitive low voltage signal like this.

 

Ben's right on about those vampire taps. Also you can't use them on the O2-sensor wire because it's a double-shielded coaxial cable that runs to the DME. You'll have to tap into the O2-sensor wire at the sensor itself or before it plugs firewall connector.

Even then I can't imagine you would get a better signal to the AF-ratio display running your own unshielded cable vs. Porsche's double-shielded coax cable. They used that special cable for a reason and no other wires in the entire car has that kind of shielding. So I wouldn't bypass it, just tap into the O2-sensor signal at the DME connector.

As for having to run a ground directly to the battery, this indicates a separate problem that you have: bad ground straps. If you have a better AF-ratio display by runnning your ground directly to the battery, what about all your other instruments that are grounded normally? Like the dash, and DME/KLR computers? What good is an accurate display if your computers aren't running properly and getting a "pure" signal? So fix that other problem of bad-grounds separately and use the grounds at the computer itself so that your display will show the AF mixture that your computer itself is really using.

 

good point on the ground issue. I originally just grounded my a/f to the chassis, but when redoing the O2 sensor and a/f connection, i grounded directly to the batt just to be safe, given that a friend here in houston did have a problem where the car ran fine, but the a/f didn't read properly. from a limited test period (I just redid the a/f a few days ago) it seems the readings are about the same, so I guess my ground was ok)

As far as vampire taps go, I would agree they are sub-optimal. However, I did use one on my old O2 and it worked fine while I had it set up that way(tapped between the sensor and the plug to the harness). Over time, however, I would agree there is a good risk of losing a good contact simply due to the fact you are cutting into the O2 wire in a fairly crude fashion.

By connecting upstream of the harness plug, you should also still be able to get a signal even if you unplug the O2 from the harness in an attempt to get the car to run richer (although if I remember correctly, when running with the O2 unplugged, I still didn't get a good a/f reading even though I tapped in upstream of the plug)

 

ok - im screwed i think. I tried using vampire type tap on the signal wire and found out that way that it is double-shielded coax cable. I didnt get a signal to my guage and now Ive got that wire messed up. How do I reconnect the double-shielded coax cable correctly?

Thanks,

Mark

 

You have to strip back the shielding and splice the connections together. If you haven't done this before, might want to get a help. To do this correctly, you will need a solder the connections back together.