Over the weekend I changed the transmission in my 2002 GMC Sonoma / CrewCab / 4wd / 4.3l / 4L60E. When I re-installed the battery I was able to start the truck a few times. When I went to put the truck back on the ground, it would crank but not start. I tried plugging into it with my OBDII scanner and the scanner would not connect. I also noticed that there is no fuel pressure at the Valve on the Fuel inlet side of the intake manifold. Is it possible that the ECU is not commanding the fuel pump to turn on? The ECU is an LS1-B and the next step I was going to take was to bench test the ecu with EFI live and or my OBDII scanner. If anyone has any insight on this, it would be greatly appreciated.

 

Try and command the Fuel pump on with the scan tool in EFI live..

or you can try and using a jumper wire from 87 to 30 in place of the relay..

make sure the fuel pump is working and that should let ya know if its antitheft or not.

 

Thanks, I'll give this a shot when I get home tonight.

 

Fuel pump will turn on even if vats is aggarvated. Check the grounds on the back of the block on cylinder heads. See if the check engine light illuminates KOEO.

 

Check Engine Light does illuminate when the key is on with the engine off. I was assuming it was due to the O2 sensors but for some reason the OBDII port will not communicate with my scanner. It seems like the truck has locked me out of the diagnostics.

 

you check fuses??

i know on the silverados the cig lighter fuse is blown.. no OBD power.

 

Does the scanner power up but will not communicate?

 

Yes the scanner powers up and when I select "read Codes" it comes back with a message that says failure to communicate, check connection. The connection is fine, I believe it is just not receiving any data.

 

Update: So I plugged in a GM Tech 2 diagnostic scanner this weekend and found out the truck thinks it is currently in 3rd Gear. The dashboard however is reporting that it is in Park and the transmission is physically in Park. I am thinking that the neutral safety switch has shorted/gone bad. Does anyone have any thoughts on this?

 

Fuel filter replaced. Truck now starts.