awesome! Yes great idea...I was just asking this dude from jeep dealer tech same questioquestions... let me tell you something...i called 3 dealerships..guess what..i knew more then they did. One flat out told me. "No clue". I just got off phone with this other idiot that really had no clue and I asked him " what about communication wireing to pcm? He says " oh. Yea u can do that i guess. Idk." Ridiculous! They also wanted me to bring my jeep in. I said " why? You cant hook up your " do ya job for you " code reade . And apparently you really dont know wtf im even talking about. Why would i waist my time lol
but yea great advice. I guess i gotta get volt reader now and find out what has to be what. I think i know were groud wires are but have no clue where the pcm is? Lol

 

Ok ive been at this 2 months and 5 days...and up all night doing more research. I need a break b4 i end up 302ing myself for a week lol. Thanks all im gonna get some sleep but please keep advice and great info comming! Im gonna get this no matter how long it takes lo . Unless i win lottery and pay someone to "just do it" I would say get a new jeep but I would never! The new vehicles these days are computers on wheels! I wanna tottaly restore my jeep someday and if i ever buy a 2nd vehicle. Its gonna be from 80"s on down... computers are no good!!!

 

When you say "no clue where the PCM is?" do you mean the PCM component itself or a particular wire or node on a connector?

The PCM (engine computer) on your 99 is a metallic box located on the drivers fender.

 

Don't concentrate on the whole big picture all at once. Take a few breaths......

Focus on one thing at a time. First, focus on how to correctly use a voltmeter. Watch online videos on how to correctly use one of these tools. This is needed to be done in order to help you to find the problem. Doing this could provide you with lifelong valuable knowledge, to use again and again... I apologize if you do already know how to correctly use a voltmeter? But, if you don't really know how to correctly use one of these? Well...

It is usually good advice to go after known problems first and foremost. You have one definite issue you can certainly go after right now, and I think to do this first would be wise. There is supposed to be power and you know it, and there is not.. For right now, I think you should focus only on tracing down this one particular fault. It is going to lead you to somewhere else.. to where there is a real problem for you to see. The power not being supplied to this spot is only just the result of a problem. Tracing it out backwards from the DLC OBDII port with a voltmeter will be what ends up showing you what is the actual real fault.

If you fix this.. There is a decent chance maybe all of the other problems will auto-correct themselves, without even having to do anything further... This is not a guarantee. But, that is how these systems sometimes work.

Maybe when you investigate this know problem like that.. it could lead you back to the PCM as the primary fault? Maybe not?

If you go looking everywhere all at once, you could be taking yourself around in circles and looking at illusions. You have got to go at it with a plan. I think the plan should be to start with trying to figure out why you have no power going to the spot where you know it should, but is not getting there for some reason? Find and figure out the reason for this...

 

I think the problem is basically electrical. in nature. The headlight switch could have done extensive damage.You could have a bad pcm also. Try and figure out what works and what doesn't. trace the wiring. and be patient.

 

my 1st best guess is that along with blowing the fuse, that surge of current can toast one of your wires, be it fused and shorting, or open.

therefore, I would systematically test the relevant wires on that circuit for continuity or short, as suggested by a previous poster

not an easy task, the circuit and pinout diagrams from the FSM are essential

 

Being a person who works with electricity, the toughest thing to troubleshoot when you can't look at it and touch it, is electrical issues. If you can't get it resolved on the internet then you should seriously consider taking it to a reputable shop. The problem can probably be found in less than an hour.

 

No reverse lights and not shifting into OD, certainly points to the NSS sensor. It's likely not connected to your problem pulling codes and the instruments since they aren't connected. Power to the NSS for the reverse lights comes off a major circuit, that if it were dead the engeine wouldn't be running. The trans computer connects directly to the NSS to read the position, and not through a data bus. Did you adjust the NSS properly when you reinstalled it? Did you check if you had voltage on the NSS connector on the +12 for the backup lights? Are the backup bulbs actually good? I honestly have no clue why jumpering voltage to the OBD connector seems to help overdrive (you mean 4th gear or the torque converter lockup, btw?).

Check ALL of the fuses. In particular fuse 17 in the underhood power dist center, and fuse 11 in the inside fuse box. You need to figure out why you have voltage at the headlight switch but not the OBD connector. The 1997 and 1999 service manuals I have show a tan/black wire that goes directly from the OBD connector pin 16 connector to pin 4 of headlight switch connector. Possible you melted or damaged the OBD connector or headlight switch connector or wiring? Mucking up the OBD connector will affect the data link bus and prevent the instrument panel from getting data.

It is pin 16 you're jumpering power to right? Jumpering power to one of the data lines will definitely cause things to not work correctly. I suspect when you start the vehicle without your jumper the gauges read correctly, and then stop updating when you jumper power to the wrong pin.

 

Yea it is the 16 pin im jumping to. All fuses are good, inside and under hood. I checked f17. And yes overdrive, i guess thats 4th? Wirks fine only when i connect my jumper.
it shifts fine but will not go anymore then 3rd gear, like 25,000 rpm at around 50 mph.
just strange about my gauges not working while jumpet connected.
Well this is awesome advice from everyone! Thank you! I now have a direction to go in..I guess first my dad is bringing me his volt reader Saturday and get down and dirty checking but i need to know the correct voltages and where. I especially wanto check wireing from the DLC to pcm to start. Also Voltage from NSS to backup lights. Allot to do! Im so determined. Im sick so i probably wont work again on it till Saturday.
please keep the great advice coming tho!
If you guys think of anything else just let me know. God bless!

Justine

 

I see there are two imperatives, in no particular order;

1) - The wire in the DLC with a loss of feed power to it.
2) - The headlamps fuse circuit.

Those are where your problems are most likely going to be found. You should find out what all is on that headlamps fuse circuit. You can turn your headlamps on. Then, pull out its fuse. Naturally, the headlamps should turn themselves off after you do this pulling the fuse. Next, put this fuse back into its spot on the fuse panel again. Look near to where this fuse panel is located to find some bundled wires that are on individual connectors. Start pulling these connectors off one at a time, until your headlamps turn off... After you find out which one of those wire bundles is associated to the headlamps fuse in that way.. you will then know the exact wires that are tied into this headlamps fuse circuit by doing that, and you can begin to test them with a voltmeter from there. One or more of them may present a problem for you to see? Use a manual for referencing the wires by way of their color if you want, so that you will know exactly what it is you are actually testing when you use the voltmeter on those wires. You will also need to know the specifications, so far as voltages and all of the rest of that goes for these wires too. I don't know what all may be on this circuit? I would definitely want to find a wiring diagram of this circuit, in order to be able to see it from the right angle. It could be anything forward or afterwards to this circuit was possibly effected.. I doubt it is before the fuse though, but who knows where that current exactly went when it surged?

 

Awesome Noah! This will be the first thing ill do Saturday. That makes way total sense. In meantime ill continue research and study schematics.