Vehicle Theft Security Hood Ajar Switch - Operation

OPERATION

LATCH MOUNTED

The standard equipment hood latch mounted hood ajar switch is actuated by the hood latch mechanism and the hood latch striker. When the hood is closed and properly latched, the latch mounted hood ajar switch is an open circuit. When the hood is open or only partially latched, the hood ajar switch is a closed circuit. The switch has a 1 kilohm diagnostic resistor connected in parallel to the switch contacts located between the two switch terminals. The hood ajar switch is hard wired in series between a return circuit and a signal circuit of the Body Control Module (BCM) (also known as the Common Body Controller/CBC).

The BCM reads the hard wired hood ajar switch input through an internal pull-up resistor, then uses this input to control other electronic functions and features of the vehicle. Some of these features may include the remote start system and the Vehicle Theft Alarm (VTA). The BCM may also send electronic hood ajar switch status messages to other electronic modules in the vehicle over the Controller Area Network (CAN) data bus.

The latch mounted hood ajar switch as well as the hard wired inputs and outputs of the switch may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information.

STAND ALONE

The plunger of the optional stand alone hood ajar switch is actuated by a molded plastic striker secured to the underside of the hood panel inner reinforcement as the hood panel is closed. When the hood is closed and properly latched, the hood ajar switch is an open circuit. When the hood is open or only partially latched, the hood ajar switch is a closed circuit. The switch has a 1 kilohm diagnostic resistor connected in parallel to the switch contacts located between the two switch terminals. The stand alone hood ajar switch is hard wired in series between a return circuit and a signal circuit of the Powertrain Control Module (PCM) (also known as the Engine Control Module/ECM).

The PCM reads the hard wired hood ajar switch input through an internal pull-up resistor, then uses this input to control certain features of the start-stop system. The PCM may also send electronic hood ajar switch status messages to other electronic modules in the vehicle over the CAN data bus.

The stand alone hood ajar switch as well as the hard wired inputs and outputs of the switch may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information.