[Chevalier]

Hi all, trying to diagnose a mystery jeep. 04 grand Cherokee 4.0L bought at a police auction, with no key and no history. Replaced ignition cylinder with a new dorman unit which allowed the ignition to come on and the jeep starts, showing 187K miles. After a couple of seconds, vehicle shuts off. Assumption is SKIM unit providing the cutout. Got a local locksmith out to program a new transponder key, but he tried two different scanners to program the key and neither would connect to the pcm. I tried checking with my bluepoint code reader, it also showed 'no codes' but also couldn't read any info off the pcm. Acted like it wasn't connected, although the physical connection was good. I figured the next step was to replace the pcm, but my concern is that there might be some other issue between the OBD port and the pcm since the pcm is at least working enough to allow the car to start and then shut down..... Any suggestions on how to "talk" to the pcm? If a new pcm is in order, any suggestions on who to deal with? Anything else to check first before trying a new pcm? Thanks in advance for any suggestions.
Regards,
Dave

 

[jtec]

it starts, and is acting like a SKIM issue.

Does the CEL come on at each start for @ 3 seconds then go off?

What happens when you try the key on off 3x trick?

Check cavity 16 of DLC for 12v.


try sending a PM to 'waterluvr' a forum member with a good knowledge of SKIM issues and hopefully some ideas.

 

[Waterluvr]

Data collision is an issue on the Chrysler pci bus tech, lot's of people with consumer grade OBD scanners that work well on most anything can't connect to a Jeep pcm so don't overthink it.

The best in aftermarket OE level diagnostic tech utilizes a 16 pin Chrysler data collision adapter at the data link to clean it up and make it work on the difficult ones.

That aside, sounds like there's more to the story here since your getting a start/run/shutdown the pcm and skim module aren't communicating the required security data on the bus to override the security.

OP if you happen to be close to me send a PM and we can get together and I'll bench test the pcm you have, you can even try your own scanner on my bench test and programming harness to see if it connects that way.

I can also program a plug and play loaner PCM for you to drop in there for troubleshooting needs as well.

This is what I use to connect to a pcm on the bench top:

 

[Chevalier]

So, first thanks JTEC for the suggestions, I'd forgotten about the key trick.

CEL doesn't go off. After about 10 seconds it begins flashing, but stays on.

Tried the key 3x trick and it came back with a P0123 code and and P1685 code. The 0123 is a throttle position sensor and the P1685 is a skim code

Not familiar with "cavity 16 of the DLC" what is that?

Waterluvr, thanks for the info, I'm down in Texas, so not too close (need to update my profile....) working on this for a friend, haven't had any similar issues with my 99 wrangler Down in our neck of the woods, lots of vehicles got flooded with Harvey, so certainly can't rule out that the vehicle has gone swimming at some point in its past. There seems to be a bit of extra corrosion when I pulled the center console to be able to disconnect the transmission interlock so that I could load up the vehicle before I was able the swap in the new ignition cylinder. The vehicle was able to move under its own power. at least 2 or 3 seconds at a time since it does fire up until the security system kicks in. Just trying to identify issues before ordering a known good pcm.

Thanks again for the input.
Dave

 

[Waterluvr]

So I just went back over your original post, I wonder if the lock smith knew what they were doing? The key's aren't programmed to the pcm, the rf id code for the key resides in one of the 8 memory locations in the skim module and he would have needed the pin code to access key programming mode in the skim module and I doubt you had that number available to give him?

There are pin code pullers, did he use one first to retrieve the 4 digit pin number out of the skim module?

 

[Chevalier]

The locksmith had two different programmer/scanners. We discovered the lock cylinder I had replaced only had steel keys (Dorman 924-703), so he cut a new transponder key to fit the new lock cylinder. After verifying the new key was transmitting (using a socket built into one of the programmers), he was trying to read the skim unit to get the code. This was through the OBDII port. He said his machines weren't connecting to the vehicle {"not seeing it"}, so he couldn't flash the skim or pcm. At that point he said there wasn't anything else he could do, we both assumed it was a pcm issue, so he said call him when I had the issue resolved and he could program the new key.

That is what had me wondering if there was a break in the communication to the pcm, so I plugged in my OBDII code reader (Bluedriver) and it wasn't showing that it was even connected to a vehicle, even though there were clearly codes being thrown.

As a side note, the locksmith was there for almost an hour going back and forth between the two scanners and cutting the new transponder key. When I asked what I owed him, he said just a $15 trip charge and he was tossing in the transponder key since it was already cut. I tossed him a bit extra since he had clearly tried everything he knew to try to get it to work out.

A further note, the vehicle was able to move under its own power, for at least a couple of seconds at a time until the skim kicked in, so verified at least the basic drive line wasn't seized up

Thanks again for the input.
Dave

 

[Waterluvr]

Dave, if you'll send me a PM with your contact info and email I can get you set up with a loaner pcm, skim module, lock cylinder and programmed security key that will all be drop in plug and play just pay the mailman for his time.

That will eliminate all the loose ends of the tech issues and if you don't have a turn key Jeep at that point there is a wiring issue on the bus that's going to have to be found and repaired. If it fixes the issue you can keep that in there and send back the old pcm you have and I'll flash update and skim program it for you and you can send the loaner back when your all done.

The loaner pcm will cease to function after about 4 weeks so that leaves you plenty of time to get it in and drive a bit and or troubleshoot the bus wiring if needed.

 

[jtec]

A SWAG or call it a hail mary, ASSUMING the locksmith was competent, I am thinking the communication issue was with SKIM,
Lets look at the SKIM module MY thinking if that was not communicating the locksmiths scanners could not do their job. They often have frayed, loose damaged wires within several inches of connector.