I've got a 5.3 in what used to be a V6 98 chevy truck. When I turn off the key it runs for 2-3 more seconds and then dies, and then it re-primes the fuel pump. Any ideas? I simply took the wire from the old pcm that turned the fuel pump on, and connected it to the new pcm's fuel pump relay enable wire.

Any help is appreciated

 

You need to have a relay in there. Check for any type of electric motor wired directly into an ecm supply.(like an electric fan or fuel pump) When the key is turned off those items will act like a capacitor/generator and keep the car running.

 

It started doing it when I hooked up the electric fans. Thank you VERY much

I was thinking I should start separating my power supply and relay setups. I though I was being clever when I did what I did, and now I'm thinking that I would be a little better off to change it. No big deal to chance, cause it is all still mock wired to test functionality and I have to pull some apart and run them in their final arrangement anyways. Thanks again!

By the way, it uses the stock truck's relay, I just changed it to where the new PCM enables and disables it rather than the original.