Door Switch: Description and Operation

DOOR AJAR SYSTEM
The door ajar, tailgate and flip-up glass ajar states are used as inputs for the Body Control Module (BCM). The BCM uses these inputs to determine exactly what position the doors, tailgate and flip-up glass are in. The DRB III will display the state of the door ajar, tailgate ajar and flip-up glass ajar switches in Input/Outputs. It's important to note, that when any door, the tailgate or flip-up glass is closed the switch state on the DRB III will show OPEN. When any door, the tailgate or flip-up glass is open the switch state on the DRB III will show CLOSED. During diagnosis, if a door, the tailgate or flip-up glass is closed and the DRB III displays the switch state as CLOSED, it indicates a shorted ajar circuit. If a door, the tailgate or flip-up glass is open and the DRB III displays the switch state as OPEN, it indicates an open ajar circuit.

The door ajar switches are located in the door latch assemblies.

DOOR AJAR SWITCH
This vehicle has four door ajar switches, one for each door. Each switch is concealed within and integral to its respective door latch unit. The switches are momentary leaf contact-type units that are actuated by the door latch mechanisms. A short pigtail wire and connector on each door latch connects the door ajar switch to the vehicle electrical system through its respective door wire harness. The door ajar switches cannot be adjusted or repaired and, if faulty or damaged, the door latch unit must be replaced.

The door ajar switches are actuated by the door latch mechanisms. When a door is closed and properly latched, its door ajar switch is an open circuit. When a door is open or only partially latched, the door ajar switch is a closed circuit. The door ajar switches are hard wired between a body ground and the Body Control Module (BCM). The driver side front door ajar switch is connected to the BCM through a driver door ajar switch sense circuit, while the remaining three door ajar switches are connected to the BCM through a passenger door ajar switch sense circuit in a parallel-series arrangement. The BCM reads the door ajar switch status through an internal pull-up, then uses these inputs to control many electronic functions and features of the vehicle. The door ajar switches can be diagnosed using conventional diagnostic tools and methods; however, for proper diagnosis of the BCM, and both the hard wired and electronic BCM outputs affected by the door ajar switch inputs, a DRBIII scan tool is required. Refer to the appropriate diagnostic information.

Fig.4 Hood Ajar Switch:

Fig.5 Hood Ajar Switch Striker:

HOOD AJAR SWITCH
The hood ajar switch is a normally closed, single pole momentary switch that is used only on vehicles equipped with the Vehicle Theft Security System (VTSS) for sale in certain markets where it is required equipment. This switch consists of a molded plastic body with a molded plastic mounting bezel. The switch body has an integral molded connector receptacle on the lower end, while the spring- loaded switch plunger extends from the upper end. Two external latches integral to the mounting bezel lock the switch into a keyed mounting hole in the stamped steel switch mounting bracket. The mounting bracket is fastened with two screws to the right inner fender shield near the fender ledge in the engine compartment. A molded plastic striker with an integral retainer and mounting tab is secured to the underside of the hood panel inner reinforcement to actuate the switch plunger as the hood panel is closed. A single take out of the headlamp and dash wire harness connects the switch to the vehicle electrical system. The switch receives a path to ground at all times through another take out of the headlamp and dash wire harness with an eyelet terminal connector that is secured by a ground screw to the left inner fender shield in the engine compartment.

The hood ajar switch cannot be adjusted or repaired and, if faulty or damaged, it must be replaced. The hood ajar switch striker is not intended for reuse. If the striker is removed from the hood inner reinforcement for any reason, it must be replaced with a new unit.

The hood ajar switch is normally held open as the spring-loaded switch plunger is depressed by the striker on the hood panel when the hood panel is closed and latched. When the hood is opened, the spring-loaded switch plunger extends from the switch body and the switch contacts are closed. The hood ajar switch is connected in series between ground and the hood ajar switch sense input of the Body Control Module (BCM). The BCM uses an internal resistor pull up to monitor the state of the hood ajar switch contacts. The hood ajar switch can be diagnosed using conventional diagnostic tools and methods.