How to open up 99 PCM

[taylorb]

I believe I have some bad solder joints in my pcm on my 99 xj? I am having a IAC p0505 code, the new iac didn't work, sometimes the check engine light goes off when I restart it after drive awhile then stopping for a bit. It seems after the computer soaks up some heat it works. I have tested the wiring and it is all good, so I am down to the PCM, so if I have to get a new one, I might as well see if I can fix it. I was wondering how to get into the PCM, do I just take the screws out and run a razor blade around the edge?

Thanks

Taylor

[jeepster_259]

u can't open it. my 98 pcm was bad, so after i replaced it i opened it up to see how it works. u will destroy it by opening it. after opened, i plugged it back into my jeep for hahas, absolutely nothing. do urself a favor, look on ebay and the forums for a 97-99 pc,. i just actually sold 1 from a 97 for $35.

[taylorb]

Thanks for the info. I guess I will leave it alone. The part number for my pcm is a 99 only thing so I will probably have to get a reman, since I haven't found one with the part number I need. The Jeep still runs fine, just have to give it a little when you start it when it is cold, so I will probably just live with it.

Thanks

Taylor

[jeepster_259]

i learned the hard way that part #s don't need to match. just make sure its from a 97-99 xj w/ same engine and tranny and u r good to go. i'm running a used pcm from another 98 w/ different part #s, runs fine. dont' listen to the dealer, they will try and tell u that it needs to be reflashed for $150. IT DOESN'T. just plug it in! i learned this after lots of research and finally listened to someone on this forum.

[taylorb]

Thanks for the heads up on that. That makes things a lot easier. I guess if it does not work, I can just sell it.

Taylor

[taylorb]

Do you know if the mileage that the odometer show, if it is stored in the computer or not?

[jeepster_259]

mileage is stored in ur gauge cluster, so u don't lose anything w/ switching comps.

[taylorb]

I got a pcm from a 97 fixed my problem I was having with the IAC. I am having a problem with the oil pressure gauge not working, it just goes up to the first hash mark and doesn't more, looks like 97, 98, and 99 all have different part numbers for the oil pressure unit. So it looks like I need to fine a computer out of a 99.
I also tried to open up my old computer since I am going to run the 97 for now and see what you mean about you can't open it, the circuit board is attached to the case of the pcm.

Thanks

Taylor

[taylorb]

I looked in both the 97 and 97 FSM and it looks like I can wire in the a 97 oil pressure sensor, so all I need is the pigtail for the 97 and the sensor. I needed a new oil pressure sensor anyway and the 97 is cheaper.
I thought I would post this so if anyone else had the same problem.

Taylor

[jeepster_259]

glad it fixed ur problem! the oil pressure gauge not working is just a minor issue imo to have such an easy fix as swapping out the computer. my swapped computer gives me a constant CEL, but w/e. you probably could bring it to the dealer and have them reflash the comp. for $150 to match everything w/ your vehicle if you really want to waste money!

[taylorb]

I also realized my cruise control doesn't work anymore after the computer swap. I am just going to keep looking for a ecm out of a 99 XJ, and then sell the 97 ecm I have.

Thanks

Taylor

[jeepster_259]

that's the only thing, u have to make sure the computer is from a vehicle that has the same options as yours. so it seems the comp you got was from a vehicle w/o cruise control. if you can find one w/ all ur options great. otherwise it's a small inconvenience.