ECM Swap-ability? Same year, mismatched ECM numbers.
#1
08-12-2019, 07:27 PM
Join Date: Aug 2019
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ECM Swap-ability? Same year, mismatched ECM numbers.
Howdy, new user here -- I've got a 1995 Ram 1500 automatic 2wd Shortbox with the 5.2 v8. I've had her for about six years now, and slowly, over the course of the past two years or so, it doesn't want to start without a 2-3 minute wait.
(I did my best to search through posts here, but the forum doesn't allow you to search for ECM -- It says it's too short a search term.)
I've got to turn the key on once or twice, and wait... Eventually, one of the relays starts clicking rapidly like a card in bicycle spokes. Over the course of about 30 seconds, it starts slowing down, and eventually starts flashing the check engine light in time with the relay clicks. Once the clicking stops, the check engine light goes out and it'll fire up immediately. If I try to start it without waiting, it'll crank perfectly, but never start.
On another forum, I found a guy who had the same exact problem, but only if it was cold outside. He was actually able to remove the ecm, bring it into the house to warm it up, and have the truck start normally. Mine does it all the time now.
I grabbed one at the junkyard the other day for $30, but the numbers don't match up. The ECM in my truck is an 56028078, and the junkyard one is 56028321.
The junkyard truck was also a 1995 automatic 5.2 V8, but it was an extended cab 4x4.
Online searches show both numbers as being valid ECMs for my truck, -IF- the ECM numbers match.
This link suggests that the last two digits of the ECM number are just software revisions, and that they should swap ok.
https://www.epartsland.com/products/...puter-56028078
Any danger in plugging it in and trying it out?
Thanks!
-Al.
#2
08-12-2019, 09:23 PM
#3
08-13-2019, 12:17 AM
See if the magic smoke comes out 
Well I hope not, it shouldn't. But did you figure out which relay is having an issue ? The auto shutdown relay (ASD) and fuel pump relay apparently are controlled together by one pin on the ECM on the older trucks. Might be worthwhile checking the wiring between the PDC and ECM and if pin 51 at the ECM provides a good ground for the relay control lines.
Well I hope not, it shouldn't. But did you figure out which relay is having an issue ? The auto shutdown relay (ASD) and fuel pump relay apparently are controlled together by one pin on the ECM on the older trucks. Might be worthwhile checking the wiring between the PDC and ECM and if pin 51 at the ECM provides a good ground for the relay control lines.