After much cursing and yelling, my jeep is running again. Why is it so special?

Because it got the very last ECM in Jeep Dealer inventory in the whole United States. I don't know how many 2006 Unlimited Rubi's with the 4.0 and a stick were made, but they had better hope their computer can be repaired if it goes bad cause there just ain't another one left in Jeepland.

It all started with a sudden die while driving to town 6 weeks ago. Engine shut down, guages went flat (as in no power), turn key to start and it would just crank, never fire. Turn key to off and then to start and away it goes with a cam shaft position sensor code. It would run for a little bit then repeat the death cycle. I got it back to the house by restarting and getting as much speed as I could and then coast.

Really confusing issues....... gave me a headache. After a few days I sent it to my mechanic (boy was he happy with the description). He did some of the same things I tried and got no further. We finally decided the code was not real and the issue was a short with a wiring harness. I even spent an hour and half with him one morning after work pulling and tugging and checking and scratching our heads. Could not get a replication consistently. Finally he accidently bumped the ECM with an elbow reaching for the main harness at the back of the engine. Boom! There it is! Bad computer........... (In my head I'm saying very bad words.)

Our local auto parts house, O'rielly's Automotive, contracts with Blue Streak/Steam/ I don't remember the name for sure; to do computer repair at about one third the price of a new computer from the dealer. Only it's a three week lead time. We get it back after four weeks and he tests it out. They even flashed it as part of the deal. Works great. un all over town. Let it sit and idle in his parking lot. No problems. I got about two miles away from the shop and the Jeep died. Same problem, turns out they didn't fix it because it worked fine after a five hour shake test. But they didn't have it powered up when they tested, so no heat buildup.

Evidently the discussion went downhill and my mechanic went looking for a new computer which he found. THE LAST ONE. Will they get more made? Who knows? If the gravel roads that I live on beat this new ECM to death I may have to ................ well I'm not sure what.

Evidently there is enough difference in the years that a ECM from 2005 wouldn't work. At least that is what the dealership is saying. I have my broken ECM. I can't decide if i want to try to have somebody else repair it or take it apart to see what the real problem was or just use it for target practice or frame the darn thing and hang it on the wall.

Thanks for letting me vent a little.

You are welcome. I even read your entire post. You are welcome again.

Thanks! Some times the Irish in me comes out and I get windy. Probably should have put this somewhere else, maybe Off-Topic?

I'd crack it I open and have a boo. What the heck...

Nah, it's fine here.

Curiosity got the better of me and I did a little searching on ECUs and PCMs. I was always under the assumption the circuit board(s) were potted in epoxy or some sort of resin due to the harsh environment. Vibration and extreme heat-cool cycles are murder to electronics and circuit board lands.

Apparently the Jeep PCM is not potted and somebody familiar with soldering and working with surface mount components could take a stab at "rebuilding" a PCM. I suspect "rebuilding" is actually reheating solder pads and a close inspection of the board under a microscope looking for cracked traces. Then the shop probably re-flashes the PCM and hopes for the best.

Actually performing diagnostics on a PCM would require lots of specialized test equipment, specifically a logic analyzer/decoder and a good working knowledge of the PCM. Whoever builds the PCM would have a test jig and a complex program that checks every function of the PCM.

If you take the PCM apart - post some pictures for us.

"If you take the PCM apart - post some pictures for us."


Absolutely, please post

If the info is correct that the board is not potted, then yeah, I'm going in there when I get a chance to figure out how to open it up. It's gonna have to wait for a bit............. I have to figure out why my wipers don't work now. I would do it tonight, but there are a lot of skeeters outside and I'm tired of swatting at them while I mowed lawn today.

Hey John, You confused what "potted" is?

Thanks for taking the last one, I have 2 6 speed LJs LOL

Not to worry, I got a call from my mechanic. They (dealer) wanted the old PCM back as a core. So I didn't get to crack it open and see inside but somebody will probably get it fixed and put it on the shelf to sell.

Here's hoping neither of us needs it........