Theory Of Operation

WARNING: This page is about a different car, the 2017 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

The Body Control Module (BCM) provides a reference voltage on the Hood Ajar Switch Sense circuit to the Hood Ajar Switch. The reference voltage then travels through the Hood Ajar Switch and back to the BCM, through the Sensor Ground circuit.

When the Hood is closed, the Hood Ajar Switch is opened. The BCM sends the reference voltage to the Hood Ajar Switch and through an internal 500.0 Ohm diagnostic resistor that is in parallel with the Hood Ajar Switch. The reference voltage then travels through an additional internal 500.0 Ohm resistor, on the Sensor Ground circuit side of the Hood Ajar Switch, through the Sensor Ground circuit and back to the BCM, which pulls the remaining reference voltage low.

When the Hood is open, the Hood Ajar Switch closes and the internal 500.0 Ohm diagnostic resistor is bypassed. The BCM reference voltage sent to the Hood Ajar Switch then travels through the internal 500.0 Ohm resistor, on the Sensor Ground circuit side of the Hood Ajar Switch, through the Sensor Ground circuit and back to the BCM, which pulls the remaining reference voltage low.