Theory Of Operation
A single Hood Ajar Switch is used on vehicles without Engine Stop/Start (ESS), e-Torque or Plug-in Hybrid Electric Vehicle (PHEV). Two Hood Ajar Switches (Hood Ajar Switch 1 and Hood Ajar Switch 2) are used on vehicles with ESS, e-Torque or PHEV.
This diagnostic procedure is for the Hood Ajar Switch or Hood Ajar Switch 1. For diagnostic information regarding Hood Ajar Switch 2. Refer to DIAGNOSTIC CODE INDEX .
The Body Control Module (BCM) sends the position status of the Hood Ajar Switch/Hood Ajar Switch 1, through CAN Bus messages, to the Powertrain Control Module (PCM).
The BCM monitors the hardwired Hood Ajar Switch/Hood Ajar Switch 1 through the Hood Ajar Switch Sense circuit, along with the Sensor Ground circuit.
The Hood Ajar Switch is normally open when the Hood is closed. When the Hood Ajar Switch is open, the reference voltage travels to the Hood Ajar Switch and through an internal 500.0 Ohm diagnostic resistor, which is internally parallel with the Hood Ajar Switch. The reference voltage then travels through an additional internal 500.0 Ohm resistor, within the Hood Ajar Switch. The total resistance of Hood Ajar Switch in the open position is approximately 1000.0 Ohms.
When the Hood is opened, the Hood Ajar Switch closes and the internal diagnostic resistor is bypassed. The reference voltage sent to the Hood Ajar Switch only travels through the internal resistor. The total resistance of Hood Ajar Switch in the open position is approximately 500.0 Ohms.