I have a 2004 Trailblazer and I need to replace the motor. I bought a second hand motor for it but the new motor has a sensor at the bottom of the base pan that my old engine does not have. Does anybody know what this is for? Or more importantly does anybody know what I need to do in order to add/bypass this sensor to my vehicle? Unfortunately, I do not know what year vehicle the new engine came out of. Any help would be much appreciated.

 

By the way it's the 4.2L engine

 

I would try hooking up every thing you have and see if it runs without computer errors.
When I bought my 2007 there were no gauges working. There was a crappy super tuner installed in it I took it out and found wires cut everywhere. I tried to find a harness from a wrecked trail blazer, could not find a complete one. So I got the dash wiring from a Chevy front wheel drive mini van and then I bought all the heat shrink and solder that a local radio shack had in stock. I went to work cut soldier splice until I got every connector wired I replaced the radio from a GMC envoy no extra wires that went nowhere finally everything works. Except the stereo LOCKED....

 

my engine has a sensor on the bottom I do not know what it does but my trail blazer is a 2007 the wires disappear into a harness going up to the top area of the engine

 

if the engine has it but your truck does not if that is the only difference try changing the part that does not have the sensor from your old engine