Stop Lamp Switch Diagnosis for Isuzu Isuzu MD Steel Tilt (F Model) 1998

1. Connect the trailer air lines, if equipped, to a known operating trailer.
2. Block the vehicle wheels.
3. Start the engine.
4. Charge the air system to the governor cut-out point.
5. Apply the system park control, the trailer air supply, and the tractor park controls, if equipped.
6. Turn the engine to OFF.
7. Ensure the following:

•	The brake lamps should illuminate when either the foot brake or the trailer air brake control is applied.

•	The trailer air brake control and the foot brake should operate the trailer service brakes when applied individually.

•	If either of these switches does not function, replace the faulty stoplamp switch.