ok so I did a diagnostic test and seems my 02 sensor is out of range. I plan on replacing it but would it be the upstream or downstream? all the code tells me is that it's bad... but which one lol...

 

The code should tell you, what code did you find?

 

96 only has 1 by the cat, I think.

 

Year? It's important...

1987-1990 has only the one in the exhaust collector.

1991-1995, I think, has two - one in the collector, one after the cat.

1996-1998/1999 has definitely two - one in the exhaust one after the cat.

1999/2000-2006 will have at least three - one before each cat in the exhaust manifold, at either one after the main underbody cat or one after each pre-cat (I don't recall.)

The cats closest to the engine are there to provide feedback for fuel trim, the ones after the catalytic converter monitor catalyst efficiency. However, the code should tell you which one is out of range - "Bank 0" and "Bank 1" refer to either driver/pax or fore/aft, and "Sensor 1" is the "upstream" sensor, "Sensor 2" is the "downstream" sensor. So "Bank 0 Sensor 1" would be the upstream sensor on the front half of the manifold on the 6-242 with the #0331 head.

This is why it's so useful for you to give with the basic information on your vehicle - particularly since 1974, everything's changing almost constantly (it's been getting faster in the last 10-15 years or so...)

 

96.. sorry for the slow response I am at work. I'll have to recheck the code but I believe it was 21 but don't take my word on it until I can post it again tomorrow from home.

 

*bump*

 

In order to properly troubleshoot this, we need the POXXX code that can only be obtained with a code reader or a scantool. I am assuming you are getting the 21 code by performing the "key-on, key-off" retrieval technique. That works, but does NOT give you the full code that will help you narrow this down.

The 2 digit code 21 is a legit code, but the 2 digit codes are too vague.

Know that this condition can be an O2 sensor, but it can also likelyl be something like a vacuum leak or an exhaust leak that is changing the fuel/air ratio and creating a condition that cannot be properly compensated for with the oxygen sensors.

I'd get the full code if I were you and post the EXACT number here for comment.

These oxygen sensor codes are commonly "misdiagnosed". I have had more than a few where the owner has replaced the oxygen sensors and the code/cel still exists.

 

1996 should be OBD-II. SAE standard OBD-II codes are five digits - a letter and four numeric digits following (and zeroes are important.)

Your HEGO code should start with a "P" - for "Powertrain" - and look something akin to "P0133" - which is the code for "Upstream HEGO response slow/heater failure," in this case. The alpha digit tells you what system, the first and second numeric digits tell you what system, and the third and fourth tell you the specific failure (as I recall.)

Yes, you can get a two-digit numeric code from OBD-II, but your DTC21 comes back to several different SAE OBD-II codes - P0125, P0131, P0132, P0133, P0135, P0137, P0138, and P0141. So getting the full code is going to save you an awful lot of work.

OBD-II code readers are relatively inexpensive in the aftermarket (I paid sixty bucks for mine - my OBD-I kit was $150 on sale, but it had adapters for GM, Ford, and Chrysler...) and are simple to use. OBD-I was mandated by CARB with no particular interface standards, but SAE took over for OBD-II and made several industrywide standards to make things easier for us all.

 

BOTH! and go all out and by the 4 wire heated ones. its about 110/ea. but if your gonna do one, ya might as well do both and not skimp on quality! just my .02...

 

agreed on getting both.
I didn't think the key on/off worked for obd2? I used the method for obd1 and t worked...
I'll look for a scanner thanks guys.

 

Heated oxygen sensors have been in OEM use for about thirty years - it's a lead-pipe cinch he's got heated sensors anyhow. But, don't replace a three-wire with a four-wire, five-wire, or six-wire - replace it with what came out of it, only newer and a good brand (I like Bosch - they invented the thing anyhow - or ACDelco. Nippondenso for weeaboos, Bosch for eurotrash. And yes, they do make six-wire sensors now - they're used in newer German cars...)

OEM for the XJ would have been Bosch - it's what Chrysler used before, and it's what Daimler/Benz used when ChryCo was owned by them. I'd be only mildly surprised to find that ChryCo still used Robert Bosch AG parts all over the place - they're usually good quality stuff.