Disconnect the main cable connector of the key switch and, using a tester, check the internal switch connections as follows:
Turn the ignition key to the OFF position and check that the tester goes to the end of the scale range across points (1) and (4) (not connected).
Turn the ignition key to the ON position and check that the tester goes to the end of the scale range across points(3) and (6) and across points (2) and (5).
Turn the key to the PARK position and check that the tester goes to the end of the scale range across points (1) and (4) (not connected) and across points (3) and (5).
Turn the key to the LOCK position and check that the tester goes to the end of the scale range across points (1) and (4) (not connected).