New XJ owner, getting some codes

Well, here's the deal... My wife decided to "surprise" me and purchased an XJ without letting me take a look at it first :doh: . the body is in excellent condition, but it runs a little rough, and loud, and the check engine light is on. I checked the codes via the key on, off, on,off, on method and here's what i got...

code 12 - Battery input to PCM disconnected during last 50 key starts.

code 21 - Problem in the oxygen feedback circuit.

code 17 - Engine running too cool.

code 41 - Fault in the charging system or no field current.

code 55 - Completion of fault code display.

i verified the codes 3 times, but oddly code 17 was displayed AFTER code 21, which doesn't seem right to me, i'd think it would display 17 then 21.

i figure the code 12 was whoever she bought it from trying to clear the codes before she looked at it. 21 could be the oxygen sensor needing to be replaced, or i'm thinking it could be reading inacurately due to the hole in the exhaust also. code 17, i haven't had the engine completely warmed up, would this matter? and 41 i'm guessing would be a problem with the alternator?

the exhaust is held up with wire in a few places, there is a hole in the muffler which makes for the loudness, but i think there are also a few exhaust leaks in other places, sounds like some ticking under the hood which i'm hoping is only a leak. the hood release doesn't pop the hood so i'm working on that currently, if anyone knows a trick to pop it that would be great.

other info: the odometer shows 169494 miles, has an auto tranny, inline 6cyl, 4WD, 4DR

i'm new to these vehicles so any advice/assistance on getting this thing up to par would be greatly appreciated. thanks in advance!

the code 17 is probably the t-stat broken. the pcm wants the engine to warm up with in a certain amount of time based on the outside temp. if it cant do it with in a few drive cycles, it will set the code.
the 41 is probably the alt.
if you've only got small leaks in the manifold (or pre-02 sensor) i would guess its the sensor.
as for the hood, good luck.

This will help with your hood problem

http://www.comancheclub.com/forums/viewtopic.php?t=872

If you get the hood opened, but some pb blaster on the cable out towards the front of the hood. As for your codes, I can offer some help.

Cody hit on a few things correctly. Obviously the PO didn't know how to clear the codes, and allow the engine to go to its original settings, and begin again. Do a search, as I also didn't notice what year this XJ was, so I cannot help you there. The engine running too cool is correct. If you unplug the sensor connector on the T-Stat housing, it should kick the electric fan on almost immediately, provided the engine was running. It will set a code as well, I think a 22, whichever one that indicates a fault with the fan circuit. The 41 is most likely a bad alternator. I would have the charging system tested at any parts store or you might be able to test it yourself with a voltmeter. The battery disconnect could have also been the PO doing maintenance, or the battery was even swapped or changed. This one doesn't always mean that the PO tried to pull a fast one on you. The noise you might be hearing is probably coming from the exhaust manifold, which if it has one of the old-style ones on there, it is prone to cracks on the ends where the front and rear pipes come towards the rest of the pipes. This could be leading to your running rough. Here is my suggestion. Tune it up first. Get Champion plugs, and good wires, along with a cap and rotor. Change the fuel filter, air filter, and oil and oil filter. After you have located the procedures which are here on this board-do a search for: engine code clear procedure. Clear the codes and drive it for a little bit and see if any of the ones you just fixed return. In the mean time also get ALL of the exhaust fixed, a new exhaust manifold runs about $200. I spent about $130 fixing the exhaust from the Catalytic Convertor to the tailpipe. You may need a catalytic convertor, so be prepared for some $$ for your exhaust, and don't just take it to anyplace, take it somewhere reputable. If the codes don't come back you should be good to go, then just drive it. Let us know how everything turns out.

Jeff

Thanks for the quick replies all! i guess i did forget to mention the year, only because it's in my username... but you can't always go by that i suppose. it's a 1994 model XJ for future reference.

Yea based on the code 41 i had planned on pulling the alternator and taking it to get tested first. i also planned on a full tune up with all the things ihscoutlover mentioned, as well as the trans fluid and filter, which i would do with any "new" old vehicle.

The main problem was getting the hood open, so thanks much for the great link there shelby! i'll definately give that a shot

as for the exhaust, i've been looking around to get a replacement... i plan on doing the whole system, and will be installing it myself.

i'll have to check all the wiring and connections under the hood when i get it popped, i was snooping about under the dash today and found a mess of unplugged cables also, so i'm going to have to sort that out also and make sure nothing is unplugged that shouldn't be. regarding that, there is an electronic display in the '94 models correct? it looks like there is one on the dash, but its not functioning at all, between the gauge cluster and the stereo.

anyway i'm going to try to get some of this done soon, i don't have a lot of time as i've been working long hours at the job, but i'll try to post up as i make progress.

thanks again for the great replies!

Have a look at the wiring to the O2 sensor and make sure it's not up against the exhaust. On the plugs under the dash, it's not uncommon to see a few empty plugs for options you don't have (such as the extended idle, fog lights, tranny switch if it's an auto, etc). It could be as simple as a thermostat, alternator, and an O2 sensor.

You are probably thinking what the real earlier XJs had for their clocks. If you post a pic, we might know what you are talking about. Mine has a "deadspot" area where that clock would go, on the ones so equipped. I too have found some connectors not attached, and once I make sense of them, I will post. Keep asking questions, we are all here to learn more about our XJs. I don't know a lot, but others on here can help to contribute to how and what and why, when we don't know. Check out some of my postings as well. I had some of your engine codes and repaired the thermostat-in fact, since I have owned mine, that has been one of only a handful of things that needed work. This site has been awesome with the technical things. I won't be getting rid of my XJ anytime soon that's for sure.