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O2 sensor questions

T

trust96xj

NAXJA Forum User
Location
redlands
I have the cel on for my o2 sensor. The post cat one. The computer completely doesn't read it, so I just unplugged it. Is there a fuse or relay? The one off the front is fine and functioning. Just the post. If theres not a fuse or Rlay it's got to be wiring cause my part time light dimly illiminates once the jeep is warmed up. I'm just curious and would rather just have everything functioning well even though that post cat o2 hasn't changed anything.


Also I've replaced it and nothing, so I don't know what to do. Any ideas?
 
Post cat is catalyst efficiency monitoring. It tells if your cat is working or not well enough to determine if you need to replace the cat for emmissions. Probably the cat converter is bad.
 
Year? They have a high amperage lead to an internal heater in the O2 sensor that goes through a relay and fuse. And the wires are known to get damaged, by driveshafts, exhaust and road junk.
 
It's a 96 four wire heated o2's I just can't find a diagram that'll tell what's what. The computer totally doesn't show it at all during a live scan. Shows up as n/a
 
I don't think any of the 96 jeeps had four O2 sensors, most if not all had 2 sensors on a straight 6 engine, I think, till a few years later in Calif when they added 2 more with pre cats, and duel exhausts. The scanners can be confusing, showing extra stuff that is not really there!!!!

I think I read a post recently claiming between 97-99 was when Californika added the 2 extra O2 sensors?
 
What code is it?

You will continue to have a CEL as long as the sensor is disconnected. You may even show more than 1 code now.
 
YEAR????:twak:
 
Uh... he said '96. It's a 4 wire O2, not it has 4 O2 sensors.
 
Jesh, I looked for the "96", after reading it earlier, and missed it, LOL, thanks, jumping between threads, confusion, nap time-bear hour now, :doh:LOL!!!

He nested the wording so closely, I missed it on the 4 wire, versus 4....O2 sensors, issue. Nice catch Guess I read it as 4, wire heater, O2 sensors, LOL, yes it is NAP time, LOL!
 
On a 97 there is a fuse in main engine fuse box. Mine had a cel when I bought it. Lead had made contact with the driveshaft, wore the insulation and blew the fuse.
 
I have a 4 cyl. '96. My rear sensor didn't throw a separate o2 code either.
The original behind the cat. O2 sensor had never been changed (completely ignored and overlooked).
I had an occasional CEL and couldn't pass Calif. smog because it wouldn't to go the 50 start / stop cycles to clear the code.

I finally managed to force it out (pipe wrench w/cheater), re-threaded the hole and now everything works fine. No CEL, no smog retest.
 
Sounds like you have a grounding issue of some sort, that dimly illuminated 4x4 indicator worries me.

Check your grounds - these ones are most important / relevant to this failure, I think:
* the one from the battery to the fender wall
* the one from the head bolt to the firewall
* the wiring harness grounds at the driver side inner fender - these are right between the air filter box and ECU if memory serves. Large tires with lots of uptravel can grab the back of the self tapping screw that holds the ring terminals down and loosen it up over time.
 
kastein said:
Sounds like you have a grounding issue of some sort, that dimly illuminated 4x4 indicator worries me.

Check your grounds - these ones are most important / relevant to this failure, I think:
* the one from the battery to the fender wall
* the one from the head bolt to the firewall
* the wiring harness grounds at the driver side inner fender - these are right between the air filter box and ECU if memory serves. Large tires with lots of uptravel can grab the back of the self tapping screw that holds the ring terminals down and loosen it up over time.
Click to expand...

Thanks, that's real helpful. I thought it may be a ground issue but I didn't know there was one under the air box. Thanks, buddy!
 
trust96xj said:
Thanks, that's real helpful. I thought it may be a ground issue but I didn't know there was one under the air box. Thanks, buddy!
Click to expand...
IIRC it's not quite under the airbox, but it's hidden somewhere in that area.

It runs the HVAC blower, some indicator lights, the trans computer, and some of the fuel injection / engine management system. You can thank Chrysler for that one :gag:
 
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