I have a 70 Chevelle that i installed an LS1 in about 6 years ago and ran great then last year i swapped to a 402 LS engine,it sat for a long ttime in between.Now i cant read the ecm through the obd plug it says its not plugged in,i have tried 2 different 99 ecm's no change.And fuel pump wont cycle on through relay,turns over but wont fire ?Very possibly a wire not hooked up or grounded where it should be. Can anybody help i suck at wiring,anybody on here good with this king of stuff ?

 

Does the OBD2 connector have 12 volts on it?

 

Yes 1 wire does i think orange wire

 

Then make sure the class 2 data buss wire has continuity from the connector to the PCM plug

 

BUMP anymore input