Diagnostic Overview - Hood Ajar Switches

The Electric Vehicle Control Unit (EVCU) must see both Hood Ajar Switches in the open state (hood closed) for the Remote Start and Engine Stop/Start (ESS) systems to operate. The switch states should always match if both switches are functioning properly.

• If the vehicle has a performance or correlation fault, start by determining which switch is not reading the hood states (ajar/not ajar) properly. Use one of the following methods to verify both Hood Ajar Switch states. Use the technical data information provided in the Component Functional Description and Operation to determine which Hood Switch is reading incorrectly and diagnose the switch and wiring accordingly.
  • Read the scan tool data reads.
  • Measure the resistance through each switch in both states (switch open/closed).
  • Check the voltage on the signal circuit in each state.
• Typically a performance fault against Hood Ajar Switch 2, or a correlation fault is due to the total resistance  of a switch or circuitry drifting out of range. On vehicles where Hood Ajar Switch 2 has only the one internal resistor used to detect the open switch state  , a short to ground in the signal circuit would be interpreted as a closed switch state (hood ajar) at all times by the EVCU. This would cause a correlation fault when the hood is closed/not ajar.
• Circuit Low/High faults against one of the Hood Ajar Switches are typically due to an open or short in the switch or wiring.