Big Problem after PCM Replaced
 

1998 Durango SLT 5.9L Automatic Transmission. 144K miles.

I replaced the PCM yesterday with a unit I got from ECU Exchange in Florida. They took my VIN and other stats and sent me the remanufactured, programmed PCM. I went through the removal/install procedure that was in their documentation. No problem. Took 10 minutes to disconnect battery, remove PCM Connectors and swap the old with the new PCM. Also did the security relearn procedure using the key in the driver door prior to 1st start up.
Here is what happened next: Durango started right up. I went to put enough miles on the car to be able to get it smog tested. Got a few blocks from my house and i could feel kind of a little hiccup....after which, the Check Gauges indicator came on. I turned into the nearest parking lot and parked. The Volt Meter needle was to the full left....no charge. Car stalled out. I checked the battery cables and the PCM Connectors....all secure. Alt belt shows no signs of wear. Car started up so i headed home. Stalled at left turn light and would not restart. Had to get AAA to tow me home.
This morning i put the original PCM back in. Engine cranks, but will not start. As it cranks, the Check Gauges indicator is lit up.
Reason i got the remanufactured PCM was because the Durango kept getting a P0304 code.....misfire cylinder 4. But all checks and tests for what typically cause that code to be thrown turned up nothing. Everything, including compression readings looked fine. The car runs fine and never had any trouble starting right up. Due to the timing of this problem, it seems to me that it was caused by this new PCM. But it puzzles me as to why the condition exists even after swapping the original PCM back in.

At this point I am not sure what to be looking for. So any advice or feedback is appreciated.

You can't visually decide if an alternator is good or bad. What is the battery voltage with the key on and with it off?

i never did that. only said the belt is good.

there was no compelling reason to think that the alternator suddenly went bad. i will check it none the less. thanks.

Could be a bad PCM. Wouldn't be the first time..... Voltage regulator is IN the PCM.......

The compelling reason to check the alt is that Dodge PCMs do really weird things when there is a low voltage issue, weird that doesn't make you think voltage. A bad battery or poorly working alt doesn't present them as the obvious culprit. Just trying to help based upon my personal experience. My D 'only' has 123,000 miles and the alt had to be swapped out a few K ago.

can the PCM crash/damage the alternator? i ask because the Durango started and ran fine prior to install of new remanufactured PCM. drove literally only 3 blocks before the Check Gauges light came on. After swapping my original PCM back in......car won't start and the Check Gauges is displayed when cranking.

EDIT on Jan 5th: i am sending the remanufactured PCM back to the seller. They tell me that there is no way the PCM would have caused any sort of damage to the alternator and thata my alternator is probably still good. they are going to see what is up with the PCM they had sent me and then get it back to me. Man, i hope this resolves things.

As said above reg is in PCM, bad one may have taken out diodes in alt. The guys who sell these just do a quick computer scan and call them good, I went through 3 from one of those flood car florida pcm sellers until I got a good one, replaced mine because of misfire code. first bought one said " no 12 volt to trans", second on gave me "no bus", third one worked.

thanks for the info. did this clear up your misfire code?

yes, once i got a good one, misfire code went away. The thing is, you can buy one from a plug and play site for about 225.00 and if it doesn't work, they will send another, they don't even want the first one back usually, these things cost them nothing,
The other option is find the right one in a bone yard (correct number, don't worry about letter at end that's just revision#) and take it to a dealer with the truck and have it flashed to your VIN. the cost is about the same if you shop your dealers (they don't all charge the same price).

i took the alternator out and had it tested at Oreilly's. it tested good. The remanufactured PCM was sent back and they now tell me it was a bad PCM: "...ok im sorry to say this one has an issue that was caused when the unit was sand blasted. we don't have a replacement to send so we will issues a refund in full...."

So i am now still wondering why the Durango will crank, but not start with my original PCM installed. "Check Gauges" indicator is lit and no reading from the volt meter. I will start the search process over again. But to me, it still points to the PCM having caused an issue that will not go away on its own.