OK, I'm not sure if this fits more in electrical or engine/tranny...

I just changed the transmission gasket & filter on my wife's 1999 Blazer LT -- my first attempt ever on any car. I removed the bolts, & disconnected the module on the side of the pan (w/o disconnecting any wires). Changed the gasket & filter & reassembled everything. So far, so good. I put in 3.5 quarts of ATF per the Chilton manual instructions. I started the blazer in Park, with the parking brake on. I did a fast idle for a minute or so & then proceeded to shift through each gear (P, R, N, D, 3, 2, 1) and back again. Now, the Park indicator will not light up. I turned off the car to check the ATF level. I went back to start the blazer and now it won't start. I shifted to neutral (indicator lit up) and it started right up.

So, long story short, I'm thinking a sensor problem or something leading it to not detect that it is in Park. But, I'm not really sure what is causing it. Any ideas on what it could be?

Thanks.

 

supposed to check trans fluid while the truck is running and the transmssion is hot

 

Alright. car MUST be running,hot,in park before u can check fluid. if its overfull,remove bottom cooler line and runa hose off it into a bucket,have friend start truck for just a few seconds as it will fly. only remove a bit at a time..

anyways,onto the sensor. I have no idea what year it started but gm put a gear selection sensor on the side of the trans (black box) well they tend to wear a grove and when you remove the sensor without polishing it down it can kill the sensor. Might be time for a new one.