1997 Chevy 2500 van. Truck running in Drive. As soon as I take my foot off the brakes it clunks and dies. It does NOT do it in reverse. Pulled ABS fuse, unplugged ABS module. Same thing. Only thing new (to me)ECM from a 97 pickup with the same motor.

Did it do this immediately after swapping ECM'*?

My first guess would be to check to see if it is attempting to engage the TCC to lock the torque converter when it happens.

Makes no sense why it would be doing that, but it'* where my gut says to look first.

If you know what to look for, and have a tach on the dash, you can probably figure out if that'* what happening pretty quickly.

Yes, I am going to put the old ECM back in this morning and will update post.

Yes, I'm going to put the old ECM back in this morning and will post results.

That is exactly what it feels like. If I bring the rpms up it will move until I take my foot off the throttle.

UPDATE: It'* the ECM. I put the old one back in and the problem went away. New question. What would happen it I removed the brake input to the ECM? This is just a beater I use around the farm. I replaced the ECM because I had no 5v reference for the MAF. Would be happy if I could get either one to work.

If the other devices have their 5 volt reference you know it'* not the ECM.
I can get the service information if you need.

The only code I get is MAF signal low and I have no power on pin 28 in the Red connector? (yes I pulled the wire to make sure it wasn't shorted to ground)

Which engine?