I have a 2004 LQ4 in a 1967 Chevy truck. According to the diagnostic machine there is power while cranking but as soon as the engine tries to fire (you can hear it fire a few cylinders) the computers turns off then immediately back on for some reason. Do you have an idea what would cause the computer to turn off/on when the engine fires off? BTW the indicator light comes on when the key is turned on but goes off during crank, any ideas?

Thanks

 

Do you also have battery power going to the pcm?

 

Yes I have battery power to the pcm.

I should also state that the truck was starting and running but I unhooked the computer to rework the mounting bracket and now it will not start. Any chance I damaged a pin when I replaced it?

 

Sound like that could be your problem.Could be a loose connection.

 

Did you find the problem?

 

Does the original bracket before you reworked it look like it gets a ground from the chassis to the case of the PCM? Perhaps by reworking it has lost the ground?