Why does my truck turn off when I put it into Drive or Reverse? on 1993 Chevrolet 1500 Pickup

"I own a 93' chevy silverado, & the problem is, my truck turns on fine but then when i try to put in into Reverse and press the gas it turns off, & tried it with Drive but it does the same thing. Can it have something to do with transmission?" I had a mechanic look at it and he unpluged something close to where the oil pan is, and now it drives fine. What could be the problem?

Asked by for the 1993 Chevrolet 1500 Pickup
the sensor costs about 30-40 buks.. it should be located on the front of the valvebody..
What is this sensor called? Transmission sensor? All help would be appreciated, thank you very much.
2 more answers , 2 more comments
torque converter lock up/ he disconnected the conveter. you can do that on the old trans. i am surprised he did not tell you. this is temporary. with it disconnected there is no lubrication to the main shaft. this will fail the trans in a short period of time.

Thanks i am gonna check it out
my 1993 chvey subabun has the same probblem i turn it on and it idles fine but whe i put in drive it will turn off unless i keep pressing the gas
Any luck with figuring out the problem? I'm having the same issue with my 93 Sierra pick up.