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Searched searched and serached! Used pcm where to re-vin?

1K views 8 replies 4 participants last post by  Loud Pedal 
#1 ·
Having some problems... have a 1996 3500 4x4 47re. Truck was having trans problems, tc lock wouldn't work, and cruise control inop. Found that the pcm was bad. Replaced with a used pcm of the same truck/ part number. My concern now is that it didn't fix anything and my abs/ brake light is now on.
My question is that because the used pcm has not been cleared and or updated for this current vehicles vin. Could that be the cause of the problem? Also any one know where I can get this used pcm cleared so I can reflash it with the current trucks info? Any help would be greatly appreciated! In dire need of help.
 
#2 ·
if it was from a 1996 47RE Cummins, then you should be fine.

If you replaced the PCM, and you continue to have the exact same problem, the cause is likely elsewhere.
 
#3 ·
Thanks for the reply. I didn't know if the pcm not being coded for the right vin was at cause. Because now I have an abs and brake light on when I didn't before...

My transmission problems are, now with the tc lock up switch on and trans relay jumped that the truck won't shift past 1st gear. With that disconnected and relay back in. The tcc lock seems stuck on and the truck has ZERO gov pressure on the snap on scanner... at a complete lost here.
 
#4 ·
PCMs are not VIN coded. The ABS is not controlled by the PCM either. A troubleshooting checklist for autos has been posted several times, and more than likely the factory service manual (FSM) has one also. The FSM also has ABS troubleshooting. How did you find "that the pcm was bad"?
 
#6 ·
I'm having a few issues. Which is my reasoning the pcm was bad, but doesn't mean I'm right. The trans tcc wouldn't unlock according to the scanner. It made my truck feel like an absolute terd. It dyno 635, 1303 in OD so it shouldn't take 10 seconds to do a 0-60. The truck almost has a slip/hit/tc lock-unlock feeling when shifting. The gov pressure shows 0, trans temp shows -83*, cruise control doesn't work, od off button doesn't work, horn doesn't work, and the truck won't go out of 1st gear with the tc switch on. I have checked the trans wiring and it seemed fine, new tps, BRAND NEW TRANS, I'm at a lost. Thank for the reply everyone hope to get closer to fixing this.
 
#7 ·
Obviously you haven't cracked the FSM to find PCM outputs. Apparently you are a part of the new breed that relies on some type of computer to diagnose problems. I suggest you get a new truck if that is the case. These are old trucks, scanners for the most part are about worthless, it takes a human brain to find a problem. The only output for trans temp is just to trip a warning light, and there isn't a pressure signal at all. The PCM has nothing to do with the horn. A multi-meter, a wiring diagram, and time (maybe a lot of time) is in order.
 
#8 ·
Thanks Games for the reply. Too bad that I've been through the FSM MULTIPLE times. Hence the reasoning why I made a post..My finds are quite different, sometimes ill have good voltage and then neXT time i check i wont. Its intermittent (spelling). Which is why I purchased a used pcm.. I work on this truck for maybe 20 minutes a day so its not typically something I can spend hours doing diag on. As I have 5 other vehicles to drive. And I work full time, and have school full time...
WEIRD BUT GOOD NEWS... the gremlins seem to be fixed for now... All I did was pull batteries off over night, reinstalled the new to me pcm and all the errors are gone... my cruise control works, gov pressure shows, OD button works, etc... The only thing I need to do is have the pcm flashed so my tc lock up will work..
The whole point of this post was to find out why I was having such intermittent issues... it would work then it wouldnt. Sorry to be a bother of you Games... I have had this truck torn to frame and back so it does get quite sickening trying to find issues..
 
#9 ·
PCM flash has to be done by the dealer....
When I had mine done, the quote was 100. (hour shop time). I negotiated down to 50 because I was bringing it in for two recalls at the same time. The good news is they did not charge me for the flashing because the took an extra day to do the "half day job" they stated...the bad news is the flash (though they said it was successful, did not fix the issue.
My advice, get them to agree they can fix the problem or no charge...
I dislike dealers a bunch (based on personal experience)
 
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