Q: Where is the transmission speed sensor on a 2003 Pontiac Bonneville

Hi There, As you know, there are two speed sensors. One is an input speed sensor and one is an output speed sensor. These are both very different in terms of their location. The input speed sensor (which is what I believe you are referring to) is located inside the transmission under the side cover and requires the transmission side cover to come off in order to access. This is a fairly labor intensive job and usually requires about 4-5 hours to complete. In order to remove the side cover, the transmission will need to be tilted down slightly which requires the sub frame to also be tilted down. I would suggest having a professional from YourMechanic come to your location to assist with this job should you need any additional help.