Putting the car in Park or Neutral prevents the engine from starting; if the engine starts up in any other gear, check the Park/Neutral switch first because a bad one or poor adjustment might be the issue. Raise your vehicle and stand it on jackstands, taking off the electrical connection from the Park/Neutral switch. Verify switch performance by measuring connection resistance on the switch's side of the connector when key is off, using an ohmmeter; adjust if possible and test again before accepting the need to replace faulty switch. First, put your in-center shift lever into Neutral position. Lift up the vehicle, prop it on jackstands, then loosen the electrical switch's holding bolt. Align the notch and neutral connection points, hold the switch this way, and tighten the bolt. On T100 vehicles, to replace the system, loosen the oil cooler pipe clamps, disconnect the oil pipes, unfasten the Park/Neutral position switch cable plug, pull off the lock washer, and loosen the switch's holding nut. To replace the Park/Neutral switch, loosen the holding bolt and switch here in the reverse order you removed it ensure the switch works correctly when installed.