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redwrangler1994 12-31-2010 09:21 AM

94 yj PCM toubles
My 94 yj wrangler 2.5L 4 cyl wouldn't start. I pulled a plug and checked but had no spark. So far i have replaced the rotor, the dist. cap, ign coil, dist. pick up sensor, (CPS) crankshaft position sensor and I still dont have a spark. everything cranks fine and I also have the smell of gas out the exhaust. when I turn the ignition on, I only have the seat belt indicator lamp and brake light. These lights are normal but i dont have the check engine light or up-shift at any time or other warning lights. I checked all fuses under the dash and also the fuse box infront of the battery both visually and with a continuity tester and they are all good. I also exchanged the auto shut down cube, but i still dont have a spark. I dont have a computer error code unit to use.
I unplugged the 60 plug wiring harness that goes to the pcm and have tested the ones that seem related to my problem including cavity 4,5,9,11,12,20-24,32,44,54, and 57. I tested for voltage always hot, Ignition on, and cranking.
Im confused as to why K19 (ignition) doesnt have voltage always or ign on, but do have while cranking. I would think it should always have voltage to K19.
At 21-24 i dont get a test light. should I?
Can someone explain to me how to properly test for the 5 volts at sensors please?
Can you please help me trouble shoot it from here. Trying to get this going with my dad and were going crazy!!! Please help with any trouble shooting suggestions. Thank you VERY much.

hannahuffster 12-31-2010 09:42 AM

You dont need a computer to to read touble codes on a YJ. you key on and off 3 cycles on the ignition switch and read the flashes of the check light. There are a lot of threads here that discuss this. BUT a bad ECM will not show a fault in the trouble codes. Since you have replaced all these parts have you checked to see if you have fire at the coil? Also the ASD relay doesnt stop the ignition system - only the fuel pump.

I have had this exact problem on my 93 - 2.5 in the past and have found no way to test the PCM other than replacing with another with the same part number (there are multiples - make sure and check before you commit to purchase), and it seems you are about to that point.

Do make sure and pull your power distribution center and check for any burnt spots on the bottom - and around also double check your ground.

redwrangler1994 12-31-2010 09:47 AM

DO you know where I can find out what pcm numbers are compatable with mine which is 56028289

sevenservices 12-31-2010 09:51 AM

A little over a year ago I put in a rebuilt PCM after a lot of similar trouble. Best thing I ever did...

If you pop the cover on your computer there might be a group of resistors and capasitors that are all crapped up in there. The failures usually spread in clusters of cooroded parts on the mainboard. Look for those, if you pop the cover and there are nasty spots, have it rebuilt or replaced.

hannahuffster 12-31-2010 11:57 AM

From what I understand they are part numbers and do not interchange at all. Different years used sensors with different wire configurations and different low voltage(s). In addition motor type / trans. type and etc factor in to the computer's functions. I found my computer at a salvage yard in Washington state (I am in MO) after days of hunting. There are some companies on-line that rebuild (a core charge type of thing) them for <seems like> around 200$. You might get lucky and find one on ebay or maybe even at a local salvage yard, but I live in what seems like the salvage capital of the world and had zero luck finding one local. Wrangler parts dont hang around long in those places...

sevenservices 12-31-2010 04:31 PM

I responded to the duplicate post,

hannahuffster 12-31-2010 04:49 PM


Originally Posted by sevenservices (Post 956552)


Garyk 12-31-2010 05:30 PM

There's a write up here somewhere about replacing the capacitors.

redwrangler1994 01-01-2011 08:49 PM

Thanks for the support on WF

redwrangler1994 01-01-2011 09:37 PM

Looking to buy a R&R pcm. I've looked around and have found is this a reputable website or would you recomend a different site?
Thanks, looking for a 56028289.

NAVYCHIEF 01-02-2011 02:06 AM

go to Auto Computer Exchange - Auto Computer Superstore - Cheaper than dealers and mechanics.

they program what you buy to your vin and milage. 1 yr warranty.

sevenservices 01-04-2011 02:42 PM


Originally Posted by NAVYCHIEF (Post 959039)
go to Auto Computer Exchange - Auto Computer Superstore - Cheaper than dealers and mechanics.

they program what you buy to your vin and milage. 1 yr warranty.

x2 Thats who I used back in '09... very pleased with it. :punk:

redwrangler1994 01-12-2011 12:38 PM

Thanks for the help. When I got the pcm, i plugged it in and the jeep started right up!

sevenservices 01-14-2011 10:43 AM


Originally Posted by redwrangler1994 (Post 984327)
Thanks for the help. When I got the pcm, i plugged it in and the jeep started right up!

hell yeah, another one back to life!!! :punk:

backbonejay 08-25-2012 09:47 PM

Powertrain controle module
I havThane almost the exact same problem, only I have no power going to the ignition coil. The wires are in good condition. One go's to the power dist. box to the auto shutdown relay, and the other go's to the computer, PCM,

I changed the ignition switch hoping that would send power to the coil, but no luck.

In the run position, should'nt the hot wire come from the relay, and the open/close power come from the computer after it's running?

I checked the relay and it's fine, but I thought when the igniton is on run, the wire in the relay box should come hot but it's not. Does it sound like a bad computer, or a problem in the relay box? Also, all fuses are fine.


Driller 08-25-2012 10:13 PM

most likely is a pcm problem. if the check engine light does not come on when you try to start it is most likely that. on fleabay you have several choices some that charge 61.00 up to over 300.00. the cheaper ones just fix the problem with the check engine light starting issue. the others give warrenty for 1 year up to as long as you own the vehicle. or you could just get lucky and score one cheap with the same numbers and options at a salvage yard. good luck... Driller

backbonejay 08-25-2012 10:52 PM

Thanks, but shouldn't the power be sent to the coil from the wire that comes from the relay? When I turn the ignition to the on position there is still no power at the coil connector.
any suggestions?


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