Engine computer question

[RSchwarzli]

Was asked a question today and I need some background.

Guy blows up engine on 2005 2500 automatic. Wants engine from boneyard. Gets another 2005 engine. Does he use the bone yard ECU or the old one from his now blown engine?

Logic dictates that the ECU from his existing one goes onto the new engine as long as it is known to work with the PCM. Or is there a serial number mismatch now that would be present?

According to Chrysler's system while looking under his VIN and the boneyard trucks VIN, it shows same PN for both the ECU's.

Said blown engine owner said that last time he tried this, he required the ECU on the donor engine as that is married to the engine and must stay with it. Without it the engine didn't work.

So, given that, my mind says his issue last time (was dealing with two 2004 engines) was that likely was two different 2004 CPLs hence his issue. But I am curious as it is a question I don't know the answer to and that annoys me. LOL

Thoughts? Can someone give me a crash course on ECM and swap-ability?

Thanks!

Robert

 

[AH64ID]

He should use the original ECM.

 

[RSchwarzli]

I agree. But why?

 

[AH64ID]

The VIN is programmed into the truck, I believe that new ECM's need to be programmed to work in a truck.

 

[RSchwarzli]

Is the ECM programmed with the VIN too? Or just the PCM?

 

[AH64ID]

I thought the ECM was too, could be wrong thou.

 

[JR]

Logic would say as long as the engine ratings were the same it shouldn't matter (SO vs HO).

At least that's how it is with the 2nd gen fuel systems.

 

[Bob4x4]

The Ecm goes with the truck-not the engine.The ecm holds info the truck needs.The ecm on the 5.9 crd doesn't need to be tied to the engine.The 6.7 needs the injection correction codes but that's about it

 

[cerberusiam]

The 2004 and 205 trucks don't have a PCM, all the engine, chassis, and body controls are contained in the ECU. The actual implementation is done by different modules but the ECU provides the signlas to achieve operation.

That said, there is a range of part numbers in all the years that the replacements need to adhere to to have the correct hardware configuration for the software. The ECU holds the VIN as does the sunsidiary computers and whne they do not match you have problems. Always use the ECM that comes with the truck or you WILL have to have the replacement ECU programmed with the correct VIN for the truck. Part numbers are only needed if the ECU is being replaced, otherwise it stays with the truck.

He had a problem with the previous ECU's if an ECU had to stay with the engine, specifically the original ECU was bad. The actual engine does not care what ECU is controlling it, just that it does so in a way that allows it to run. Notice I said run, not run correctly. You can drop a 04.5 into an 04 chassis, and vice versa, and both combos will run just not correctly because of the differences in spray angles, timing, pistons, etc. It does not matter what the power ratings, designation, etc, what has to happen is the fuel needs to be injected at a point that will allow it to combust in the cyliner, that is all. It can be late, early, too much, too little, etc, as long as there is enough at the correct time to create a self sustaining combustion cycle.

 

[sag2]

The only time it would matter is if the truck has SKIM key. If it does and you swap the ECM from another truck it will start and die three times, then will no longer crank over.

 

[RSchwarzli]

That is what I was wondering! Thanks guys! Answers the questions!

Robert

 

[TGVET]

The only time it would matter is if the truck has SKIM key. If it does and you swap the ECU from another truck it will start and die three times, then will no longer crank over.

Couple years back I was having crazy codes, one dim wit Mech. said it was the ECU going bad so I bought a used out of an 04.5 (470.00), I installed it, engine only turned over, never ran. Told I needed the dealer to reprogram new SKIM. Screw that, I took it out, put back OEM ECU, returned used one, got $$ back. The electrical issues were not ECU related. Glad I never towed it to the dealer for that one and never went back to local Mech. either.

cerberusiam is the MAN !