O2 Sensor wiring - Parts and manual conflict

I'm needing to replace an old and presumed dead O2 sensor. I bout the "cheap" part requiring that I splice the wire to the existing OEM harness plug. One problem though, the part that Bosch says is for my vehicle only has one wire coming out of it and the part that's on my vehicle has 3.

The Haynes manual I have describes and shows a single wire sensor as well. So I'm not sure what's going on.

I thought it might be a california emissions vehicle, but the jeep was first registered in Maine and 2nd time was in Oregon, untill it ended up here in AZ (based on carfax).

So Right now I'm at a loss as to what to do.

Jeep is a 1990 Laredo 4.0 straight 6

Any suggestions would be greatly appreciated.
Thanks,

Holy_Handgrenade

The O2 sensor you bought is not the correct part. The Renix system does not use a one-wire O2 sensor. It sounds like you got an O2 sensor for the older carbureted XJ with the 2.8L V6 engine, or maybe the '84 and '85 I4 engine.

I've probably covered this before, but the 1987-1990 XJ w/242 does not use a "standard" HEGO sensor of any sort.

Being pre-OBD, there isn't much of a standard for them to have followed.

The one-wire sensor you have is for very early feedback systems, and is heated to operating temperature by the exhaust gas stream. Long warmup times and cranky operation is the norm - that's why the later three-wire (heated) sensors came about for fuel injection (the one-wire sensors were typically used with carburettors.)

Also, the RENIX (1987-1990 - including you) HEGO sensor is a variable-resistance type, using a titania ceramic element. This works by applying a reference voltage to the sensor, and reading the voltage after division by the variable resistance.

Later OBD HEGO sensors are "voltage-generating" types using a zirconia ceramic, and work by directly reading the voltage generated by the HEGO sensor. This won't work with the RENIX ECM.

The upshot of all this is simple - NO SUBSTITUTIONS. Fortunately, a little looking can keep the cost of the part in the $50-60 range - which is still cheaper than a lot of late OBD-I and most OBD-II units! I've been pricing them lately for my 88 (at 245K, I'm due for sensor replacements,) and I've been consistently able to keep the price between $50.95 (Discount Jeep Parts) and $59.95 (Morris 4x4 Center.) Local prices, as I recall, have been comparable.

5-90

Thanks, much appreciated. Now to convince one of these auto parts store flunkies to give me the right part

-Holy_Handgrenade

Either tell them you want OEM replacement only, pay extra at the dealer, or mail-order the thing if you've got something else to drive for a little while.

Those sources I've cited earlier are all outfits I've dealt with, and ship quickly (especially Morris!) I have no idea what the dealer wants for the thing - I try to avoid going there if I can.

Try asking for Borg-Warner OS118 or equivalent - BW does well for aftemarket parts, and I'd also use ACDelco or Bosch for this stuff. (I just don't have catalogues handy to give you the other two numbers.) Borg has yet to screw me on application listings - I've used their parts for more years than I'd care to think about.

5-90