STEP 5. Check the stoplight switch.

1. Disconnect stoplight switch connector C-03.
2. Connect an ohmmeter to the stoplight switch between terminals 3 and 4, and check whether there is continuity when the plunger of the stoplight switch is pushed in and an open circuit when it is released. See Fig 1.
   Fig 1: Checking Stoplight Switch

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
3. The stoplight switch is in good condition if the circuit is open when the plunger is pushed in to a depth of within 4 mm (0.2 inch) from the outer case edge surface, and if there is continuity when it is released.

Is the circuit is open? 

1. YES
   
   Replace the stoplight switch. Then check that a diagnostic trouble code 14 is not output.
2. NO
   
   Check that diagnostic trouble code 14 is not output. If diagnostic trouble code 14 is output, replace the auto-cruise control-ECU. Then check that diagnostic trouble code 14 is not output.