Thread: Bad Shift Interlock Module???

I have recently been having a problem with my car not starting. I have ruled out the battery, starter, and all the wiring. When i go to start my car i get a click from the passenger side dash and then i get a click from just inside the firewall on the driver side. I thought that it was either the ignition switch or the shift interlock module. I tried started my dads 3100 buick century in drive. And i got the same exact symptoms as my car. So now i am pretty sure that the problem has something to do with the black shift interlock module mounted on the trans on the driver side. I'm talking about the module that prevents your car from starting in any gear other than park or neutral. I figured id describe it since im not quite sure of its proper name. Ive checked all the connections and bolts holding it in place and everthing seems to be tight. So how often do the shift interlock modules actually fail? I'd really like to hear what everybody else's opinions are.

Thank You,
Jim P

You are referring to the PRNDL switch on the trans, the shift interlock is in the car which prevents the shifter to be moved out of park unless your foot is on the brake, hence the name interlock. If your PRNDL switch is bad you need to check out a few things. First take a test light or a volt meter and check the purple crank wire on the starter itself. Does it light up or show voltage when you crank? This wire goes into the PRNDL switch, it is the heavy gauge purple wire on the larger of the two plugs. There is also another larger gauged wire on this plug and should be yellow in color if I remember right. This is the crank wire coming from the car. If you have NO crank signal at the starter check for power here while cranking. I believe this heavy gauge yellow wire follows up onto the drivers side strut tower and is on of 3 wires on a 3 pin connector. From this connector the wires go into the car and you can trace this wire back into the car for power. I hope this helps out and let us know what you find.

Thats what the PRNDL switch is

The ignition switch ended up being the problem. Since the new one has been put in, the car has run perfectly. It even fixed my blower switch working only on 5. I thought it was the resistor, and i had just been too lazy to swap it out. It turns out that the new ignition switch made it work on all settings. I also solved my dash illumination problem as well. The cause of the problem was my a-pillar gauges. One of the bulbs must have gone out because as soon as i cut the power wire, my illumination came right on. To put it simply, today was a very successful day .

Thanks for all the help guys.

glad you could figure it out!