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2002 Jeep Wrangler Sahara
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Discussion Starter · #1 · (Edited)
Hey guys, I have an '02 Wrangler with the 4.0, MT and I'm having a major issue where the Jeep refuses to stay running.

A little bit of background. Jeep has run fine up until I swapped the belt, tensioner, and radiator. After swapping the rad, I fired it up and heard a loud screeching (definitely not normal belt squealing either) coming from the motor. I turned the Jeep off, and now every single time the vehicle is fired up, it starts pretty reliably, but it dies in seconds.

Other info that may be relevant, the Jeep does have some sort of electrical draw issue, but the battery should be good since I've added a disconnect.

A buddy and I initially thought SKIM, but after cracking open the steering column, there's no module, plus I have black skinny keys. (see photos)
We then eventually landed on a diagnosis of weak fuel pump, so that was swapped out, not fixing the issue.
We've confirmed fuel pump, injectors, spark plugs, etc are all operating normally.
We've even tried bypassing relays for ASD, fuel pump, etc as well to no avail.

We finally were able to get it hooked up to a scan tool and periodically it would throw the P1686 code for No SKIM Bus messages received.
Again, there's no SKIM module in this vehicle. What's even more confusing is everything I can find online says Jeep made SKIM standard in all Wranglers starting in 2002 (optional from 96-01). This leads me to believe the SKIM was removed, and a PCM from another vehicle may have been swapped into the vehicle.

Is there anyway to know if a PCM is stock for that specific VIN? Also, could a reflashed PCM possibly revert to stock if left without power for extended periods (battery disconnect)?
I'm kind of at a loss here. Any advice would be greatly appreciated.
 

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SKIM was not standard in any TJ as far as I know. Certainly not in my 2005 with black key & no SKIM module. The skim normally will allow it to start but die in about 3 seconds but after about 3 tries will not let the engine start at all. Also you would get the key with a slash through it icon in the cluster. So it does not sound SKIM related except for the code. And without swapping keys or the PCM it seems odd that this would happen right when you made the repairs listed. If you post the PCM part number someone here might be able to tell you if it is the correct one for your year but not VIN specific or if it had SKIM. If you get a build sheet for your VIN it might list whether it was SKIM equipped. They have changed that list format over the years so not sure if it will show that. You should be able to get the list from a dealer or email to jeep.com or similar site address after giving them the VIN.



Since this apparently started immediately after a belt change (& the screeching noise) I would remove the belt & start it to see if it will keep running. It will be OK to run it briefly without the belt especially if the engine is cold so no worry about overheating for several minutes. If it runs that way you might have a something seizing up & killing the engine. Maybe the alternator, power steering pump, idler or the new tensioner.
 

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Discussion Starter · #3 ·
SKIM was not standard in any TJ as far as I know. Certainly not in my 2005 with black key & no SKIM module. The skim normally will allow it to start but die in about 3 seconds but after about 3 tries will not let the engine start at all. Also you would get the key with a slash through it icon in the cluster. So it does not sound SKIM related except for the code. And without swapping keys or the PCM it seems odd that this would happen right when you made the repairs listed. If you post the PCM part number someone here might be able to tell you if it is the correct one for your year but not VIN specific or if it had SKIM. If you get a build sheet for your VIN it might list whether it was SKIM equipped. They have changed that list format over the years so not sure if it will show that. You should be able to get the list from a dealer or email to jeep.com or similar site address after giving them the VIN.



Since this apparently started immediately after a belt change (& the screeching noise) I would remove the belt & start it to see if it will keep running. It will be OK to run it briefly without the belt especially if the engine is cold so no worry about overheating for several minutes. If it runs that way you might have a something seizing up & killing the engine. Maybe the alternator, power steering pump, idler or the new tensioner.
The fact that your '05 doesn't have SKIM definitely gives me some relief, although I'll still check and try and get a build sheet if possible.
And I will give the beltless run a try and see what happens.
Thanks for the insight!
 

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2006 TJ Rubicon, 4.0, automatic
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My 06 doesn’t have skim either. If it does run without the belt on it, compare the old belt to the new one as well the checks RUBI 4 MY MRS listed. I seriously doubt it’s the belt but doesn’t take more than a min to be sure. I have been given the wrong belt for other vehicles before.
 

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Do you see an amber key symbol on the instrument panel when the engine dies? If so that is indicating the SKIM system has a problem like an incorrect or a dead SKIM key.
 

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Discussion Starter · #6 ·
Do you see an amber key symbol on the instrument panel when the engine dies? If so that is indicating the SKIM system has a problem like an incorrect or a dead SKIM key.
Nope, that was the other indicator to me that it didn't have a SKIM from the start. Although without tearing apart the dash, I wouldn't confirm it was the original dash. But this Jeep doesn't have many mods outside of suspension that were done prior to my purchase, so I doubt anything outside the radio was swapped out on the interior.
 

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That it starts easily but then dies every time a couple seconds after starting it still makes me think there's a SKIM related issue, like perhaps the PCM thinks there should be a SKIM system connected to it. Maybe someone installed a replacement PCM that was programmed for a SKIM.
 

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Discussion Starter · #10 ·
I had a buddy in the shop pop the belt and try to start it and still nothing.
I also pulled the build sheet and no SKIM from factory on this one. Also, thanks for the site @RUBI 4 MY MRS I didn't know those build sheets had all that info on them.

That it starts easily but then dies every time a couple seconds after starting it still makes me think there's a SKIM related issue, like perhaps the PCM thinks there should be a SKIM system connected to it. Maybe someone installed a replacement PCM that was programmed for a SKIM.
The only problem with that is I've owned the Jeep for a few years and this is just happening. I'll be checking the PCM and part numbers when I get back out to the shop.

Maybe crankshaft position sensor? Mine had a similar issue and that solved it.
I'll give this a check as well.
 

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When you removed the belt did it start, then die (as before) or not start at all?

Have you tried giving it some gas pedal to lift the idle as it starts to see if it will stay running?
 

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Discussion Starter · #12 ·
When you removed the belt did it start, then die (as before) or not start at all?

Have you tried giving it some gas pedal to lift the idle as it starts to see if it will stay running?
Nothing changed and it started, then died. I've tried a range of throttle input during start up, and it all still dies within seconds. Giving throttle will still act normally(higher rpms for more throttle), but regardless of what rpm its at, it will still die.

I'm going to check the CPS then if nothing, I'll probably go down the rabbit hole to determine what my power draw is. I guess its possible the power draw was from a short in a part that has now failed, causing the issue.
 

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How long does it stay running? If 5 seconds or less the ASD relay may be opening killing both spark & injectors. The ASD & fuel pump relays will only stay energized after initial key on for about 3 seconds, then open if the PCM is not seeing a signal from the crank sensor. The sensor could send the signal but the PCM not processing it. Since it initially does start I would think the crank sensor is good so maybe the PCM is not keeping the relays (possibly FP too) energized.

You could try pulling the ASD & probably the FP relays & with short jumper wires jump from terminals 30 to 87 in the sockets bypassing the relays to see if it will start & run. If it does, you will have to pull the ASD jumper to shut it down.

Another thing you could try first (before removing the relays) would be to turn the key to the on position, wait several seconds before turning to start. If it then will not even start briefly it might indicate the relays are not energizing since the initial energizing time has passed & now would be completely depending on the PCM/crank signal to energize the relays. If it still starts briefly you can probably rule out it starting with jumpers in place.
 

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Was there any pcm swapping done even on just a temporary testing basis between this TJ and another?

Sure sounds like your pcm got its skim function activated which can easily happen if you try you pcm in another TJ that did have a skim module on its bus


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Discussion Starter · #15 ·
How long does it stay running? If 5 seconds or less the ASD relay may be opening killing both spark & injectors. The ASD & fuel pump relays will only stay energized after initial key on for about 3 seconds, then open if the PCM is not seeing a signal from the crank sensor. The sensor could send the signal but the PCM not processing it. Since it initially does start I would think the crank sensor is good so maybe the PCM is not keeping the relays (possibly FP too) energized.

You could try pulling the ASD & probably the FP relays & with short jumper wires jump from terminals 30 to 87 in the sockets bypassing the relays to see if it will start & run. If it does, you will have to pull the ASD jumper to shut it down.

Another thing you could try first (before removing the relays) would be to turn the key to the on position, wait several seconds before turning to start. If it then will not even start briefly it might indicate the relays are not energizing since the initial energizing time has passed & now would be completely depending on the PCM/crank signal to energize the relays. If it still starts briefly you can probably rule out it starting with jumpers in place.
We tried bypassing the ASD and Fuel relay together and separately prior to the original post. Still gotta check crank sensor and a few other things though

Was there any pcm swapping done even on just a temporary testing basis between this TJ and another?

Sure sounds like your PCM got its skim function activated which can easily happen if you try you pcm in another TJ that did have a skim module on its bus


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There has been no PCM swapping done at all sine I've owned the Jeep, nor has there ever been a SKIM unit, per the build sheet. I've been too busy to get back to the shop to check if its the original PCM, but considering it has almost nothing aftermarket aside from suspension, I doubt the PCM was swapped.
 

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All including you original PCM are skim capable and easily changed to skim active

When was it in this “shop”

Sure sounds like your pcm is now skim active


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Discussion Starter · #17 ·
All including you original PCM are skim capable and easily changed to skim active

When was it in this “shop”

Sure sounds like your pcm is now skim active


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Its not a retail shop, the only two people to have touched the vehicle are a buddy of mine and myself.
All these issues started when it was parked outside my house after replacing parts on my own.
So unless a PCM can flip to skim active due to loss of power for an extended period (it sits all the time with the battery disconnected), that shouldn't be the issue.
 

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Discussion Starter · #19 ·
Then why do you say you need to check if PCM was replaced if you were there for everything that happened


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I'm only saying I wanted to check in case it was replaced prior to my ownership. I've heard of the nightmares that people go through with PMC fix companies that reflash PCM's.
I know nothing about the programming or direct operations of the PCM, so I'm trying to eliminate variables.
 
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