cmsaw83

I need to know if there is anyone out there, who is familiar enough with the use of a Power-Probe - and more specifically, using a Power-Probe on a 97 ZJ Limited 4.0L 2WD - that they might be able to provide me a crash-course in the quickest, and most reliable means of using this device to determine whether a specific circuit is, or is not shorted/faulted or otherwise suffering from symptoms related to an open-circuit situation occurring somewhere along the particular circuit, AND, how to then pin-point the specific location of any fault/short which I may have found during the previous testing/probing.

More specifically, I am interested most, in testing the ignition coil itself, and I am also interested in testing the crankshaft position sensor, and of course, the circuits related to those parts/components as well, in an effort to determine whether there is perhaps, a fault or short, which could be causing a problem that could keep my ignition coil from supplying the spark required to keep the vehicle running (or at times, even keep the vehicle from starting all together). As of right now, my ZJ will start, but in less than 30 seconds, it will stop running/stall out, and I cannot figure for the life of me exactly what it is that persistently keeps my Jeep from running as it should reliably.

As a bit of a brief history, I have been trying to get this Jeep back on the road reliably, for what has easily been 3 months now. In my effort to do so, I have replaced the PCM, the CPS, the Camshaft Position Sensor (or Pickup Coil), the Distributor Cap, Rotor, Spark Plug Wires, Spark Plugs, the Oxygen Sensors, the MAF Sensor, the Throttle Position Sensor, and the Fuel Pump, and those are just the parts I've replaced that I can recall off of the top of my head. There have been more. I have also checked my fuel injectors for proper function, and then cleaned them in spite of the fact that they were all functioning well to begin with. And the last thing I can think of, is the fact that I also performed a compression leak-down test on each cylinder (only to find that they were all within acceptable ranges). In spite of all of this, the problem has persisted. I am all but certain that it did need the PCM, and the Crankshaft Position Sensor, at the very least. Even so, I have yet to get it running to where it will run for anything longer than a week, tops. But there are times when I have gotten it running at night, only to come out the following morning, ready to head out somewhere, and realize that I am not heading anywhere at all. At least not anywhere that would require a vehicle to get to.

FWIW, there are also two larger wiring harnesses, which are located upon the firewall, just to the right of, and above the PCM, which I have begun to suspect may be a part of, if not the culprit for the entire problem. These wiring harnesses contain wires which are colored in a scheme which makes me believe that they are in some way related to the ignition coil. Another thing that is important for me to know, is which of the two contacts contained in the wiring harness for the ignition coil, is the power, and which is the GND/neutral (or whatever the other one is called!... I make no claims of being an automotive Guru, nor a Jeep Guru. I'm just a guy who works on his own cars, and who has always managed to get any broken down vehicle he has ever owned, running again.... Accept for this one....

I am officially at my wits end. I am ready to use this Power Probe thingy-majig to try and hopefully track down any shorts and/or faults which may exist in any one or more of the circuits within my Jeep's labyrinth of wiring. However, as the Power Probe is a positive, and can help to cut diagnosis times in half, or better, still, having it in my possession - as crazy as it may sound - presents its very own problem, in and of itself, which is....... The fact that I haven't the slightest of clues, as far as just how in the sam-hell one would go about using, or otherwise operating this thing to begin with. I am sure that it cannot be but so difficult, and I have every confidence that I can have some success while using this tool, but I just need for someone to help me with the details, in regard to the actual procedure involved in completing the above mentioned tasks. Any help, suggestions, or pushes in the right direction, will be greatly appreciated. Thanks in advance to anyone who may be able to offer up some knowledge/experience that might get me going in the right direction. Lastly, I already understand as much as the fact that the Power Probe must first be attached to the positive (+) and negative (-) terminals of my battery in order to supply it with the power it needs to perform it's many possible functions. I say this, in an effort to share the extent of my own knowledge, so that no one might feel the need to spend time trying to explain that much, since it has been made clear that I am all set in regard to the procedure involving the initial connection of the Power Probe to the vehicle.

Cherryokee

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cmsaw83

Done... Apologies as well, I should have had that completed a while ago, but did not even know it was a thing. Only bit I wasn't able to include, was the axle types, as I have a 2WD, and have not been able to find specific info on the 2WD models. 2WD... What's the point anyway? I needed a vehicle, and at the time, this was running, and didn't cost much. In hindsight, if I had known then, what I know now, about the terribly poor manner in which the previous owner took care of this poor old Jeep (which was really NOT taking care of it at all, not in any way whatsoever, unless you consider putting gas in it, taking care of it...), I would not have touched it with a 20ft pole.

cmsaw83

1997 Jeep Grand Cherokee (ZJ) Limited
Engine: 4.0L AMG 242ci naturally aspirated, OHV, w/ 2 valves per cylinder, and indirect fuel injection
Transmission: Chrysler 42RE 4-Speed Automatic Transmission
2 Wheel Drive

FWIW... I have already replaced the PCM (A-1 Cardone Re-Manufactured), Crankshaft Position Sensor (NGK/NTK), Ignition Coil (NGK/NTK), Distributor Cap (Accel), Rotor (Accel), Camshaft Position Sensor (distributor pickup) (not certain which brand, but it says US made on the bottom), Spark Plugs (NGK/NTK), Throttle Position Sensor (NGK/NTK), MAF Sensor (NGK/NTK), both Oxygen Sensors, the Fuel Pump, and probably a few other parts/sensors that are not coming to mind at the moment... Every time I get it started and running, it will run for maybe a couple of days, to a week tops, and then it will just randomly stall out as I am driving it down the road, at which point, I do my best to coast it into a safe place where I will be able to work on it (because I know it is not going to start up again), and it almost always gives me one code, every single time. I believe, if memory serves - which... memory does not always serve correctly - it is an 0135 - ignition coil, something or other, blah blah blah - I know the rest is supposed to mean something, but I regrettably do not know, or understand what that something is, so blah blah blah is all I've got.

So, at this point in the game, I have narrowed it down - just on pure happenstance - to an issue with my wiring, either IN, or very close around the two rather large wiring harnesses which are located just about directly to the top right hand side of the PCM (if you are standing in front of the Jeep, looking into the engine bay). I believe this is where my issue resides, because, the last few times it has stalled out, upon getting it home, or working on it where ever it was left to sit, I have payed more attention to the wires connected to the different harnesses of the sensors I've had issues with, or, that have at one point or another, thrown codes, and I noticed that a green wire, with an orange stripe, is attached to what I believe is the PWR side of the two wires connecting to my ignition coil itself, which run from the ignition coil, to one of these harnesses. Since realizing this, I have done a few different things, to include twisting the harnesses the opposite way, and then re-attaching them to their post (a plate upon the firewall with two holes for each of the two harnesses), and the last time, I zip-tied the group of wires coming to, and leading from these harnesses, together, and without replacing any parts whatsoever, was able to then start, and drive the Jeep. The last time I did the thing with the zip ties, I was able to drive it for just over a week, which is the longest time it has stayed running since I began trying to figure all of this stuff out.

When it is running, it runs beautifully, and doesn't skip a beat. It runs much better now than it ever did after purchasing the Jeep from it's previous owner. And when it stalls out, there is no pre-cursor to it at all. It just stalls out of nowhere, and that's it. Until I replace a part, or mess with wires, it will not start up and run again. I have also noticed, that I can disconnect the battery (reset the Jeep's PCM) and after doing so, sometimes it will start right up, but then immediately die before actually running for any extended period of time. This whole thing is weird, and has got me pretty convinced that I have a short, fault, or open wire in the circuit for my ignition coil.

cmsaw83

Well, no replies just yet I see. Well hopefully that will change some time in the near future. But until then, I will just keep posting any updates that I have...

So last night, before I began to un-wrap all of my wiring under the hood of my Jeep, bit by bit, I decided to have an extra close look at the wiring harness that I mentioned more than once already in this thread. It is the BLACK harness, of the pair of harnesses that are mounted just above the PCM, and to the right a bit, if you are looking into the engine bay, standing in front of the Jeep. There is a BLACK one, and a GREY one, mounted right there together, one over top of the other. And after taking them both apart, and doing a bit of further inspection, I came to realize that the BLACK one, is indeed the one of the two harnesses which houses my green wire with the orange stripe, which I see coming from (or going to) my ignition coil. Seeing as I am seeing an ignition coil related code every time that the Jeep stalls again after running for a period of time, I figure tracing the ignition coil circuit might just be a good place to start...

And sure enough... As I am inspecting the harness, after taking it apart, so that I can see into the inside of either of the two halves of the harness, I happened to realize that, for whatever reason, on the side that houses the FEMALE connections, as I pay close attention to where my green wire with the orange stripe goes into the harness, when I look at it from the inside, it is barely noticeable, but sure enough, the female terminal pin used to connect that wire into the harness, and which the male side of the harness/wiring would slide into (upon re-connecting the harness), is damaged, and this damage is noticeable, simply based upon the fact that, when comparing all of the other female terminal pins inside the harness, it just does not look the same. Upon close inspection, it became clear to me that the bottom portion of the female side crimp terminal (housed within the harness itself, and removable using the proper terminal pin removal tool) has at some point, been broken off, and is completely missing. So, it is fair to assume, that I have found at least one place which could potentially be a problem area, if not THE problem area. (if only it could be that simple, right?!) However, I cannot know for sure. I did cut the wiring on either side of the terminal, strip each side back, crimp on a red crimp terminal (like I would use to connect speakers in car audio) on each side, then found a piece of wire long enough to adequately span the relatively short distance, and crimped the opposite terminal to either end of that piece of wire, after which I connected one end, then the other, and then re-connected the large harness, so that all of those connections would be made as well, and I attempted to fire her up, with no luck. BUT!! Instead of continuing with unwrapping all of my wiring, I have decided to wait until I can run up to Auto Zone, and have the ignition coil I purchased from them replaced (seeing as how its got a limited lifetime warranty), after which, I will install the coil I know to be new, and in functional condition, and then attempt to start the Jeep again...

With the harness containing that broken terminal pin, and my ignition coil in effect, having a short, or fault within it's circuit, it is possible that the ignition coil could have become damaged again, to a point where it is no longer able to perform it's own task as needed, or when otherwise called upon. So, I would like to ensure that replacing the coil does not solve the problem, before proceeding to tearing into TONS of other wiring. Which I will only have to re-bundle and wrap again when ever I do manage to get this PITA problem solved finally! I wouldn't be so optimistic normally - especially with this Jeep in particular - but it was THIS harness in particular, which I was able to wiggle, and move around/manipulate, after which I found I could start the Jeep again at times. So, this leads me to believe that the problem lies within THIS harness, or somewhere in the very near/close vicinity to it. So, here's to hoping that upon getting my hands on the new ignition coil, this Jeep starts! Man, would that be the single best thing that's happened to me in all of 2024... A man can hope, can't he??

Cherryokee

CMSAW83, I am replying to you just to let you know that you're not being ignored. Obviously I browsed your post (and then asked for profile details).
FWIW I'm sipping my first coffee, still a little bleary, trying to absorb your story. Sadly my morning attention-span is limited and my eyes are still swimming.
Your "novel" is interesting and I think I'll read it all again in the hopes of finding the facts and questions, and then I can try to help or advise.
I think I have gathered enough from your story to restate/summarize the trouble as being related to engine warm-up status, that erratic idle and stalling occurs when the system is in "closed loop". Is this correct?

Additionally, please send a picture or full description (manufacturer and model) of this so-called power probe thingy?

Hope I can help. Please be patient (despite having to deal with this a long time) as I also have other "irons in the fire". I'll continue to monitor for your messages. If I have anything productive/helpful to say then you'll hear from me.

cmsaw83

This is the Godiag GT101 Power Probe. It is not a name brand (or "official") Power Probe, but rather, a copy of the original unit, which I purchased on Amazon, which does the same thing that the original, much more expensive Power Probe does. I'm not saying that it is just as good as the original, or anything else, other than the fact that, for me, a DIY mechanic, and weekend warrior type, this one will suffice for any needs I may have.

awg

a critical thing to establish is whether the vehicle loses all electrical power when it stalll..ie lights go out, however briefly (most easily observed at night)

If so, it will probably be a failing main battery or ground cable. A common problem

If that is ruled out, check whether you have missing spark, fuel or both when the issue arises

Do ASD and FP relay work

if your harness is not the issue, the PDC can be vulnerable to poor contacts, look underneath

Any OBD2 codes ever ?

harness wires can rub together, biggest suspects are O2 sensors, crank and cam sensors, wiring harness tight around engine bend that I think is injectors