Theory Of Operation

Without Engine Stop Start (ESS):  The Body Control Module (BCM) provides a reference voltage on the Driver Door Ajar Switch Sense circuit to the Driver Door Ajar Switch (integral to the Door Latch). A ground is provided to the Driver Door Ajar Switch through a Ground circuit attached to the body sheet metal.

The Driver Door Ajar Switch is normally open when the Driver Door is closed. When the Driver Door is opened, the Driver Door Ajar Switch closes and the BCM detects the reference voltage on the Driver Door Ajar Switch Sense circuit is pulled low.

With Engine Stop Start (ESS):  For vehicles equipped with Engine Stop Start (ESS), the Driver Door Latch is equipped with an internal Primary and Secondary Door Ajar Switch. When the Driver Door closes, the Primary Driver Door Ajar Switch opens and the Secondary Driver Door Ajar Switch closes. When the Driver Door opens, the Primary Driver Door Ajar Switch closes and the Secondary Driver Door Ajar Switch opens. Under normal conditions, with the Driver Door Ajar Switch harness connector disconnected, the voltage measured at the switch harness connector is approximately 12.5 volts (battery voltage).

• Primary Driver Door Ajar Switch:  The Body Control Module (BCM) provides a reference voltage to the Primary Driver Door Ajar Switch, which travels through the Door Ajar Switch, and back to the BCM. The Primary Driver Door Ajar Switch is equipped with an internal 604.0 Ohm resistor, along with an internal 1070.0 Ohm diagnostic resistor, which is internally in parallel with the Primary Driver Door Ajar Switch.

  When the Primary Driver Door Ajar Switch opens, the reference voltage travels through the Door Ajar Switch Sense circuit, to the Driver Door Ajar Switch. The reference voltage then travels through the internal 604.0 Ohm resistor and 1070.0 Ohm diagnostic resistor, back to the BCM, through the Door Lock Switch Return circuit.

  When the Primary Driver Door Ajar Switch closes, the internal 1070.0 Ohm diagnostic resistor is bypassed and the reference voltage travels through the Door Ajar Switch Sense circuit, to the Driver Door Ajar Switch. The reference voltage then travels through the internal 604.0 Ohm resistor and back to the BCM, through the Door Lock Switch Return circuit.

  When the Driver Door Ajar Switch is connected and the Driver Door is opened (Primary Driver Door Ajar Switch closed), the voltage measured at the Driver Door Ajar Switch harness connector is approximately 3.18 volts. When the Driver Door is closed (Primary Driver Door Ajar Switch opened), the voltage at the Driver Door Ajar Switch harness connector is approximately 6.22 volts.

• Secondary Driver Door Ajar Switch:  The BCM provides a reference voltage to the Secondary Driver Door Ajar Switch, which travels through the Door Ajar Switch, and back to the BCM. The Secondary Driver Door Ajar Switch is equipped with an internal 604.0 Ohm resistor, along with an internal 1070.0 Ohm diagnostic resistor, which is in parallel with the internal Secondary Driver Door Ajar Switch.

  When the Secondary Driver Door Ajar Switch opens, the reference voltage travels through the Driver Door Secondary Ajar Switch Sense circuit, to the Driver Door Ajar Switch. The reference voltage then travels through the internal 604.0 Ohm resistor and 1070.0 Ohm diagnostic resistor, back to the BCM, through the Driver Door Lock Switch Return circuit.

  When the Secondary Driver Door Ajar Switch closes, the internal 1070.0 Ohm diagnostic resistor is bypassed and the reference voltage travels through the Driver Door Secondary Ajar Switch Sense circuit, to the Driver Door Ajar Switch. The reference voltage then travels through the internal 604.0 Ohm resistor and back to the BCM, through the Driver Door Lock Switch Return circuit.

  When the Driver Door Ajar Switch is connected and the Driver Door is opened (Secondary Driver Door Ajar Switch opened), the voltage measured at the Driver Door Ajar Switch harness connector is approximately 6.22 volts. When the Driver Door is closed (Secondary Driver Door Ajar Switch closed), the voltage at the Driver Door Ajar Switch harness connector is approximately 3.18 volts.