If you try to start your vehicle in a gear other than Park or Neutral, the parking switch prevents the engine from starting; but if it does work incorrectly in these two positions, the problem might be from the switch either needing adjustment or failing, so start there for troubleshooting. Bump the vehicle up with jackstands, disconnect the electrical plug from the switch, and get to work. Use your ohmmeter to see if you can tell what's wrong with the connector terminals, checking again after you adjust the switch and replacing it when the issue persists. Put the shift lever in Neutral, lift the vehicle onto jackstands, take off the switch holding bolt, position the groove and neutral basic line to match, keep the switch in this spot, and screw down the bolt. To change the switch on Tacoma trucks, first take off the exhaust pipe and heat shield. Disconnect the oil cooler clamp and remove the oil cooler tubes. Lastly, disconnect the electrical wire from the switch. Prize off the lock washer and remover the nut. Then remove the retaining bolt and take out the switch. To install, you need to put the switch back in place, adjust it correctly, and test it for working properly.