Getting through the emissions test


Thanks again for the replies. I was not sure about the thread tape on the new sender so I did a continuity test on it and it was connecting with the head. I guess the thread cuts through the tape when you tighten it.
I have tested the relay off the car as well as swapping a couple of them. No problems.
I searched for a second sensor but could not find one in the rad. The boss is there just above the bottom hose connection though. The ones in the head are all accounted for.

In case you have noticed there is no visible compressor for the aircon. This is because it's under the power steering pump and the bottom hose wraps itself all round it. To change the hose takes at least a day. The pump has to come off, the compressor has to come off, the mechanical fan has to come off complete with its bracket and that's just a start. It's the worst hose I have ever had to change in my life and it's not a cheap part. My knuckles always suffer.
On the other hand the top hose is very easy.

I have ordered a new NTK O2 sensor from RockAuto just to eliminate it from the equation. Sadly the price gets doubled with shipping and duty by the time it gets here.

A couple of my friends have said just scrap it and get something newer. I could not do that, it's part of the family, anyway I have a 2004 Chrysler Sebring convertible which is great fun over here in Spain, however they are known for reliability problems which I didn't know about when I bought it. But that's another (rather long) story.

I have attached a diagram for the fan relay which seems to show that it's controlled from the ECU.
 

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does your other fan turn on when you hit the button to turn the ac on? the second fan should come on when the ac is on.

and you applied power to the other fan motor and said it works so its either some wiring from the ecu to the fan, or the ecu, like you said.

can you get all the numbers off the ecu? i haven't been able to find the one you listed
 
Thanks again for the interest. Unfortunately I can't check whether the aux. fan comes on with the aircon as it looses its gas due to a leak somewhere so the pressure switch shuts it down. It works if you bypass the fan relay, so it's electrically sound. For some reason the ECU is not bringing it on due to coolant temp. It would be incredibly difficult to test the wire from the ECU to the relay as it's buried deep inside a big harness somewhere. My feeling would be that it would be OK as nothing ever disturbs the harness.

Are all Jeep wiring harnesses as bad as the one I have got here? It looks like a Friday afternoon effort.

I have searched the area at the back of the head and the only electrical thing there is the ambient air sensor in the manifold. Where exactly should the other water sensor be? I suspect that mine might be different to a LHD car
 
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Thanks again for the interest. Unfortunately I can't check whether the aux. fan comes on with the aircon as it looses its gas due to a leak somewhere so the pressure switch shuts it down. It works if you bypass the fan relay, so it's electrically sound. For some reason the ECU is not bringing it on due to coolant temp. It would be incredibly difficult to test the wire from the ECU to the relay as it's buried deep inside a big harness somewhere. My feeling would be that it would be OK as nothing ever disturbs the harness. Are all Jeep wiring harnesses as bad as the one I have got here? It looks like a Friday afternoon effort.
I have searched the area at the back of the head and the only electrical thing there is the ambient air sensor in the manifold. Where exactly should the other water sensor be? I suspect that mine might be different to a LHD car
 
It is in the diagram posted. I doubt there is a different block for RHD vs LHD.
You could verify your new temp sending unit by measuring resistance between the connector points while the engine heats. No change bad sensor.
Check continuity at the PCM/ECU connection.
Reset ECU connectors.

Never look down on anyone unless you are helping them up - Jesse Jackson
 
Thanks for the info. There are a number of differences in the RHD version but I have worked my way through all the tests you mentioned as far as possible. My temp sensor is a thermistor not a thermostat as in the diagram so it changes resistance with temp, it is not an on/off action. I checked the new one before I put it in and it's working OK. The signal from the sensor definitely goes to the PCM and the fan relay is operated by the PCM. The only bit I have not checked is the wire from the sensor to the PCM but that's all inside the harness. I have attached a wiring diagram for info.
I have started to wire in a bypass for this by putting a manual switch on the dashboard. I'll connect into the contacts on the fan relay base and remove the relay. The aircon is not working anyway.

My patience is exhausted. I have run out of ideas.
 

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I am now actively searching for a replacement ECU.. Posting on a few parts recyclers sites have not brought any to light. I have attached a pic of the label on the side of my unit. Can anyone advise if this number is one that has been seen on any other vehicles. My XJs were originally shipped to Japan and then to the UK where I got my two. I have the temperature probe in the front of the cat that no one else seems to have, so maybe this ECU is a bit of a special for Japan. Jeep themselves have sent the factory build ticket but to temp probe is not mentioned.

Sorry but there won't be any pictures again today. As soon as I select a pic and click upload it just asks me to log in again and it keeps doing it. Am I doing anything wrong, it has worked before?
 
I have tried several times to put up a picture of the ECU label but the system won't take it. It's just a regular jpeg.

The Chrysler number I would like to find is 56028044 5602 8044. So far I haven't been able to find one and the rebuild people mentioned above don't do anything pre 1996. Thanks for the suggestion anyway.

I would like to know any details about the ECU as I think it might have been a special for the Japanese market because my car has the mysterious temperature sensor at the front of the cat. and no other car does and it has to connect to somewhere. No one can tell me that either or even what it does. Both my XJs have it, 1994 and 1995.

Does this ECU appear in any listings for other Jeeps?
 

is there any other numbers on the ecu or the sticker? one by the barcode? i cano find nothing on the number you posted except the first 4 numbers connect to dodge
 
i found this list but it doesn't go back to 94. but you should have a different pn set up somewhere on your ecu

J2534-Fedworld.xls (moparts.org)

looking on some other boards, it looks like you need a pn that starts with a p, like this: p056041 635AF




It looks like I'll have to take it off the car since it is well boxed in. That's a next week job though. Keep you posted.
I'll try the picture again but don't be surprised it it doesn't show.
 
I fitted the new O2 sensor and put the car back in for the test. That means all the sensors will have been changed. Sadly it failed again due to high CO. My next move is to fit a new cat that I have had in stock for a while. If it fails again I shall be out of ideas what to try next.
I think I'll get someone else to change the cat as I'm getting too old to be rolling around on concrete floors. The mysterious temperature sensor that no one knows anything about might be a problem if I can't get it out.
Has anyone had any more thoughts on this, like, what it is there for?
 

If your CAT is intact( not all broken up inside) and dirty you could clean it.
Again there is no OBD plug? Cause seeing the switching of the O2 can give ideas on what and where things could be wrong.


Never look down on anyone unless you are helping them up - Jesse Jackson
 
High CO is rich exhaust meaning you are not burning all the gas.
Not enough air
-dirty clogged intake
-intake valves sooty carbon build up
- intake valve not opening enough valve, spring, cam

Burning oil

Bad upstream O2 sensor

Engine in open loop not hot enough engine or O2 not hot

Stuck injector

Too much oil vapor in intake





Soo have you cleaned the intake?
Changed the O2?? NTK is a jeeps desired mfg

Cleaned the valves? Seafoam or steamed them? Run above 3300 rpm once in a while?





Never look down on anyone unless you are helping them up - Jesse Jackson
 
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