Just purchased a used ECM + PCM for my pickup. We travel a lot (including Mexico) and I want to keep a few critical spare parts on hand just in case. The donor rig was a perfect match (2002 Dodge Cummins HO six speed) for my truck and the price was right so I jumped on it. I'm assuming the ECM especially does not need to be re-flashed or anything and will be a plug and play item. Both computers are OEM off a totaled rig (121K miles....front end smashed but engine compartment looked fine). Guess I'm taking a little bit of a chance on this purchase but both computers looked great and the truck was running (obviously) at the time so they worked right up to the accident. 

Anything special I need to know about replacing the computers? I'm planning on pulling both of mine (they work fine) and keep them as my spares. I'll run these replacements until one fails. 

TNX....Mike

Some folks seem to have VIN problems when mixing them some dont. Kinf of a crsp from what l have read. No personal experience however.

" VIN problems when mixing them"

Not sure what you mean by "mixing them". The donor rig was identical to mine (2002 Ram/Cummins 2500 HO w/six speed tran). But...this is my first shot at this too which is the reason for my post. I'm hoping it's a straight swap and the ECM doesn't need a re-flash etc.

2 hours ago, MikeH said:

" VIN problems when mixing them"

Not sure what you mean by "mixing them". The donor rig was identical to mine (2002 Ram/Cummins 2500 HO w/six speed tran). But...this is my first shot at this too which is the reason for my post. I'm hoping it's a straight swap and the ECM doesn't need a re-flash etc.

By mixing l mean pcm off of one and ecm off of the other. I know you mean keepi g them in pairs but if one fails you might have to mix them and thats when the VIN match might be a problem. Maybe maybe not though.

You can try it, probably will be fine. I was told you can use them without programming to the truck for test purpose, but also heard some just put them on and get away with it.

I got a used ECM for my truck also I believe it was two months apart on built date, according to Auto Computer specialists in Florida software was different and had to be flashed to my truck. I had them reflash it everything worked great aside from my tach would quit working after few minutes. They told me it was my PCM needed to be fixed lol, I just put my original ECM in and tach started working again. Wish I would have tried it before I sent it to them to program it to my truck just to see if it still acted the same. Oh well I have a spare ECM that works fine aside from tach.

Been doing a little research and it looks like the ECM will need to be flashed with my VIN#. The PCM should be fine as is. Just wondering if a local Dodge dealer would do the re-flash or not. I'm guessing not but...

2 hours ago, MikeH said:

Been doing a little research and it looks like the ECM will need to be flashed with my VIN#. The PCM should be fine as is. Just wondering if a local Dodge dealer would do the re-flash or not. I'm guessing not but...

Just depends on whether the dealer has someone smart enough to deal with the old technology. Some seem to have no clue or no habla when convenient. All you can is ask them. 

 

Almost forgot this part, their fee.

Good news! Hooked up the PCM which worked fine. Didn't think it would be a problem. Then hooked up the ECM. Before starting anything I drained the ECM to ground to clear out any codes or memory. I've used this tactic before to turn off a pesky engine light or codes. It drains all the capacitors of energy so the ECM will have to learn your engine & APPS settings after it starts. Anyway, started the truck and drove around for 30 minutes or so and all's well. I was holding my breath on the ECM but it turned out OK. I think the trick is to find a donor rig that is absolutely identical to yours (make, model, year, engine, tranny...everything). After grounding out the ECM (google...lots of info) it should learn your truck config and be good to go. 

Still wondering what stores the odometer reading? Is it the ECM, the PCM or a collaboration of both? My rig showed the correct odometer reading after the install but I did put on the donor PCM with my OEM ECM first. Don't know if that mattered but I got the correct reading after installing both units and driving for ~30 minutes. 

Anyone know for sure which computer actually stores and keeps track of the odometer?

1 hour ago, MikeH said:

Still wondering what stores the odometer reading?

Both the odometer and the trip odometer information is stored in the instrument cluster memory.

Sort of thought something like that was going on. Couldn't quite figure out what I had done to get the correct odometer reading after installing both computers. I take it that a scan with the correct reader would still show I'm using an ECM with the wrong VIN#? And if that's so a re-flash of the donor ECM would correct the issue...right. Do I need to worry about any of this? I plan on keeping the rig so don't really care what the info ECM is holding. The only problem I can see is during emissions testing the donor VIN would pop up...right.

As the donor ECM/PCM were purchased for emergency use only (I've decided to keep the OEM computers on the rig until one fails) I can address a re-flash when the time comes. 

You can reprogram both to your vin if that's a concern. 

Didn't realize the PCM would need reprogramming also. I'll keep them as is for now...just as a backup. Thanks

They both hold a VIN number. But if yours are working mixed with the other 2 it sounds like you are one of ones that have no issue with vins not matching.

No issues at all. Again...perfect match on the donor rig. I did call a local shop today. He's checking to see if he can just rewrite the VIN. If so I'm good to go. Otherwise I'll live with it the way it is.