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Old 10-12-2012, 06:20 AM   #1
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Repair your own PCM?

Has anyone done this? Found this on another jeep forum.
I have a 2006 rubicon unlimited and I have to clear the PCM memory every few months to get it to shift smooth. Local dealer wants a fortune for a new PCM and they won't program one I bring to them. Companies who offer a reconditioned pre programmed unit have a horrible BB rating. I'm tempted to try this.


Jeep PCM (computer control unit) Issues
Before you submit to replacing the PCM (Powertrain Control Module) as the computer is properly called by Jeep/Chrysler, here is a quick tutorial on how to correct MOST problems that present as a defective unit. it requires a 30 watt (average) soldering pencil, some thin 60/40 ROSIN CORE solder (NEVER USE ACID CORE! it will destroy the unit!) and some Deoxit from Radio Shack. Deoxit is liquid magic! I have used it for decades in the electronics arena to stop erratic issues that were otherwise like chasing ghosts. It is fantastic for electrical/electronic connections in severe environments such as in an engine compartment. (No I dont own stock in the company, but wish I did!!!)

When you have your supplies together,remove the two screws in the cover and gently pry the tabs holding the covers on the PCM up. The small cover will come right off, the larger one will have to be gently pried off as it is actually the 5 volt regulator board of the PCM. This is the focus of our attention. turn it over and carefully clean any of the jelly potting compound from the solder pads of the connector strip that plugged into the other part of the unit. Now using as little solder as you can, carefully flow fresh solder onto each pad and the connector that is on the pad. It will take a bit of time to get it to flow due to the type of board material the unit is made out of so dont get impatient. when you ge a good solder joint move to the next pad inline, dont jump pads, the warming of the pard itself will speed things up. Be careful not to damage any of the components on the board or the copper traces that connect them.

When you have resoldered every pad, let the board cool, and treat the connector socket with the Deoxit... make sure yiu get it into the holes in the connector, and carefully treat the pins in the other half of the PCM where this connecter plugs into. Reassemble the unit, carefully bend the tabs back down into place. and replace the screws. WARNING! Some units have come frome the factory with screws that were too long, and eventually due to vibration shorted the unit out. I replace them with shorter sheet metal screws as standard operating procedure to avoid this issue, since I never ran into this personally.

Treat the external pins on the PCM with the Deoxit before reinstalling it in the Jeep. It is estimated that the repair I just outlined (except for the deoxit) will correct between 70-95% of all PCM problems. This is the same rebuild procedure that is done by the companies that sell the rebuilt units. As an experienced Electronics Engineer, I have gone the extra step and added the use of a deoxidizer on the connectors, which will protect the connections as well as increase their electrical integrity. I have personally used this cure myself on several Jeeps having been a longtime Jeeper with myfirst being a 76 Cherokee S. I currently have a 95 GC Limited, a 98 GC Laredo, and an 06 Wangler. You cant have just one!
As a side note on the deoxit...and this repair, my 98 GC was throwing O2 sensor errors with new sensors and irratic charging issues. I repaired the PCM as outlined and the O2 issues went away. I pulled the Alternator and took it to autozone (4 blocks from the house) and had it tested... it was fine... so I cleaned the contacts for the wiring harness and treated it with deoxit, and reinstalled... started Romero up (yes I name my Jeeps... Willie, Romero and TJ) the dash gauge indicated just under 14 volts and my DMM indicated a steady 13.81 volts and not a problem since... Like I said Deoxit is liquid magic. it should be in every tool kit if you deal with automotive electrical/electronics. It isnt cheap but it's worth it.

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Old 10-12-2012, 06:40 AM   #2
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Just a word of warning here... Unless you are an experienced microminiature technician, it is very easy to overheat and ruin the components you are working with.
Then you are going to be spending your savings on a new PCM anyway!

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Old 10-12-2012, 07:02 AM   #3
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It was a nice write up, but listen to the Navy guy.

OK - listen to two Navy guys!

Solderind on a Printed Circuit Board is difficult to say the least!
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Old 10-12-2012, 12:36 PM   #4
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I'm doing it as soon as I get some free time. What the heck! if I screw the PCM up it doesn't matter much because it's no good the way it is now. Only a matter of time before the hard shifts damage the tranny IMO. Either try this inexspensive "hopeful" fix or shell out $500.00 for a new PCM. I plan on practicing the soldering first on an old printed circuit board to get the feel of it before I do the PCM.
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Old 10-12-2012, 01:27 PM   #5
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cool- thks for giving it a try
I have access to electronic control guys at work and I know they can do the job. If you open it up post a few photo's and I can get their professional take on things. They have all the special soldering equipment. ---just an idea-- one of the guys may be interested in doing this at home to make a few extra $$$ . I can be the first one for him to do the fix and let you know what happens. I also really don't like the tranny hard shifts. Worst case I buy a new one from the dealer.
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Old 10-12-2012, 01:32 PM   #6
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Quote:
Originally Posted by koopzz
It was a nice write up, but listen to the Navy guy.

OK - listen to two Navy guys!

Solderind on a Printed Circuit Board is difficult to say the least!
Easy smeasy..
Had to solder the PCM on my sons old D350. 1/2 the pin out were rotted off. After cutting off enough resin i Did a back stab thru the board and fixed it right up. Just refilled the missing resin with clear silicone caulk.
Just like onboard ship in the gunmount, you can't break something that's broke.
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Old 10-13-2012, 09:05 AM   #7
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OK, I took the PCM off to try the re-solder fix and the PCM is filled with a clear
'Gell". I didn't see any way to solder anything! Any ideas?
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Old 10-15-2012, 06:33 AM   #8
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jeepinsc
here's where I found the original post

Jeep PCM (computer control unit) Issues
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Old 10-15-2012, 07:33 AM   #9
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Originally Posted by jeepinsc View Post
OK, I took the PCM off to try the re-solder fix and the PCM is filled with a clear
'Gell". I didn't see any way to solder anything! Any ideas?
If the 'gel' is a semi-hard coating on the printed circuit board (maybe it looks like it's been dipped in it) then it is conformal coating and will melt off when you heat the components. But it may get a bit messy. Isopropyl alcohol and a lint-free cloth will work for wiping as you work.

Like the other Navy guys said, there's a good chance you'll damage stuff if you don't know what you're doing (former Navy ET myself and have broken my share of stuff because I didn't have the right gear). If you're going to Radio shack anyhow pick up some heat sinks... they will clip on to the components and prevent damage. For more good tips you can probably search for the MILSTD 454 on google and learn the basics.

If you have more specific questions feel free to drop a line!
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Old 10-15-2012, 08:39 AM   #10
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This is also the same fix for the "Version 1", C-10 Kawasaki Concours motorcycle fuse box. The vibration from the road broke the solder joints on what is called the J-box on the motorcycle. An 1/8" drill to drill out the revits on the back cover and resolder all the connections would fix your electrical gremlins.
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Old 10-15-2012, 08:59 AM   #11
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Basically, all you're doing is heating solder joints that have gone bad due to heat, age and vibration. They've crystallized, in other words.

People really need specialized training to solder on printed circuit boards. They're very easy to damage as they're made from a very soft fiberglass/cloth medium. If it's a multi-layer circuit board, it's even more fragile.
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Old 10-15-2012, 02:47 PM   #12
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Quote:
Originally Posted by TinCocodrie View Post
Has anyone done this? Found this on another jeep forum.
I have a 2006 rubicon unlimited and I have to clear the PCM memory every few months to get it to shift smooth. Local dealer wants a fortune for a new PCM and they won't program one I bring to them. Companies who offer a reconditioned pre programmed unit have a horrible BB rating. I'm tempted to try this.


Jeep PCM (computer control unit) Issues
Before you submit to replacing the PCM (Powertrain Control Module) as the computer is properly called by Jeep/Chrysler, here is a quick tutorial on how to correct MOST problems that present as a defective unit. it requires a 30 watt (average) soldering pencil, some thin 60/40 ROSIN CORE solder (NEVER USE ACID CORE! it will destroy the unit!) and some Deoxit from Radio Shack. Deoxit is liquid magic! I have used it for decades in the electronics arena to stop erratic issues that were otherwise like chasing ghosts. It is fantastic for electrical/electronic connections in severe environments such as in an engine compartment. (No I dont own stock in the company, but wish I did!!!)

When you have your supplies together,remove the two screws in the cover and gently pry the tabs holding the covers on the PCM up. The small cover will come right off, the larger one will have to be gently pried off as it is actually the 5 volt regulator board of the PCM. This is the focus of our attention. turn it over and carefully clean any of the jelly potting compound from the solder pads of the connector strip that plugged into the other part of the unit. Now using as little solder as you can, carefully flow fresh solder onto each pad and the connector that is on the pad. It will take a bit of time to get it to flow due to the type of board material the unit is made out of so dont get impatient. when you ge a good solder joint move to the next pad inline, dont jump pads, the warming of the pard itself will speed things up. Be careful not to damage any of the components on the board or the copper traces that connect them.

When you have resoldered every pad, let the board cool, and treat the connector socket with the Deoxit... make sure yiu get it into the holes in the connector, and carefully treat the pins in the other half of the PCM where this connecter plugs into. Reassemble the unit, carefully bend the tabs back down into place. and replace the screws. WARNING! Some units have come frome the factory with screws that were too long, and eventually due to vibration shorted the unit out. I replace them with shorter sheet metal screws as standard operating procedure to avoid this issue, since I never ran into this personally.

Treat the external pins on the PCM with the Deoxit before reinstalling it in the Jeep. It is estimated that the repair I just outlined (except for the deoxit) will correct between 70-95% of all PCM problems. This is the same rebuild procedure that is done by the companies that sell the rebuilt units. As an experienced Electronics Engineer, I have gone the extra step and added the use of a deoxidizer on the connectors, which will protect the connections as well as increase their electrical integrity. I have personally used this cure myself on several Jeeps having been a longtime Jeeper with myfirst being a 76 Cherokee S. I currently have a 95 GC Limited, a 98 GC Laredo, and an 06 Wangler. You cant have just one!
As a side note on the deoxit...and this repair, my 98 GC was throwing O2 sensor errors with new sensors and irratic charging issues. I repaired the PCM as outlined and the O2 issues went away. I pulled the Alternator and took it to autozone (4 blocks from the house) and had it tested... it was fine... so I cleaned the contacts for the wiring harness and treated it with deoxit, and reinstalled... started Romero up (yes I name my Jeeps... Willie, Romero and TJ) the dash gauge indicated just under 14 volts and my DMM indicated a steady 13.81 volts and not a problem since... Like I said Deoxit is liquid magic. it should be in every tool kit if you deal with automotive electrical/electronics. It isnt cheap but it's worth it.

Sounds like adaptive strategy as far as the hard shifting goes. ECM's learn from our driving habits. Without an aftermarket tuning device, or unhooking the battery to clear what it has adapted to, your going to get that if you have been pounding on it. Not to say your ECM dosent have a problem, just saying..
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Old 10-18-2012, 06:35 AM   #13
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Quote:
Originally Posted by jeepinsc
OK, I took the PCM off to try the re-solder fix and the PCM is filled with a clear
'Gell". I didn't see any way to solder anything! Any ideas?
The gel or resin I was referring to was on the back of the board and was about 1/2 - 3/4" thick. It was soft like silicone and easy to cut out.
But this was on an older dodge pick up.

What I did to replace the rotted pins was, clean off the back of the board and clear out a solder point using a solder sucking tool. I then soldered a wire into the locations and spliced that wire into the proper place on the harness. All is did was bypass the connector.

Like everyone has said, if you haven't had training, don't try it. It's real easy to fry components. Few people have the equipment in their basement to troubleshoot a circuit board in a modern vehicle. We can check most components individually but it gets harder as the board gets more complicated.
I am a former navy gunnersmate and I'm an electrician now so after 30+ years of doing it, this stuff is easy for me. My next purchase will be a programmer. I can hook up my laptop and program building automation and equipment, but I'm still stuck twisting the key for codes.
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Old 10-18-2012, 08:43 AM   #14
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To the OP, Air Force vet here, with 35 years of experience working with wire, circuit boards, etc. If you're going to insist on what you're doing, buy a known good spare PCM first. Then proceed at your own risk.

That will keep your down time to a minimum.

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