2007 Colorado with 4.8 P01 swap fuel pump control problems

[Chrisco]

Hey Guys, I have a 2007 Colorado I did a 2000 4.8 5speed swap, I modified a factory harness to make it basically stand alone, had it in the truck running no issues for 6-8 months. Last week I go to leave work and put in a new flash as im doing some tuning on it currently. I didnt realise at the time but I changed a vcalue in the ABS speedo section which I have worked out bricks P01 pcms.

I have since got another P01 PCM and i flashed a file back that I had in the PCM before i messed with the ABS stuff, I wrote "entire" calibration file with Vats off but the PCM isnt commanding fuel pump 12v signal.

I thought it might be something going on in my Colorado fuse Panel, if I put a decapped relay in my fuel pump relay spot I can manually turn pump on without blowing fuse and can drive the truck. I pulled the fuel pump relay signal wire (green/white) from the back of the fuse panel plug and with it isolated when i probe it and command HP tuners to turn pump in it gets 12.6 for less than a second then goes off.

any ideas?
Im not sure if the new pcm doing it or its a wiring issue. its been stuck at my work for days haha

[blindsquirrel]

It's not impossible it's got a dead output pin, just unlikely. They've come a long ways from the old 1227730s ... yes, I replaced enough of them that 20 years (edit: more like 30? Jesus...) later I still remember the number.

Do a 'read entire' and save the file, then open it up and see if the VATS settings you applied survived the write process. You can also log VATS status, or something similar. Just look for anything that will say one way or the other if it's active or disabled.

Can you command the pump on in the scanner's output controls?