Circuit Description
The hybrid control module (HCM) uses the hood switch signal to monitor the open or closed position of the hood for hybrid system function. The hood switch indicates the state of the vehicle hood, either open or closed. The hood switch output signal is an input to an HCM. Five volts is supplied to the switch, the returned voltage is measured relative to HCM signal ground to determine the switch state. A resistor network in the switch circuitry ensures that shorted high and low states can be diagnosed successfully. Hood Position Condition Met indicates that the hood position, as read by the HCM, meets the HCM requirements for entry into idle engine off (IEO) hood closed. Driver Notification - Hood Ajar is used to request the instrument panel cluster (IPC) to display or clear the Hood Ajar message on the DIC. This message will be displayed by the IPC until the driver acknowledges the message e.g., via the IPC Stem, Trip, Fuel, Personalization or Select buttons on the Steering Wheel or until requested off by the HCM via GMLAN message. The HCM shall not request the message to be displayed again until the next ignition cycle if the conditions for setting the message still exist unless or until the hood transitions back to closed and then back to reopened.
Conditions for Running the DTC
| • | The auxiliary power outlet (APO) switch is requested ON. |
| • | Engine running for 30 seconds. |
| • | The HCM has received voltage on the ignition 0 voltage circuit. |
| • | The HCM has turned ON and no configuration DTC are present. |
| • | This diagnostic shall be run every 100 ms. |
| • | Reference voltage is stable and accurate. |
Conditions for Setting the DTC
| • | Hood position condition met indicates that the hood position, as read by the HCM, meets the HCM requirements for entry into engine auto stop, hood closed. |
| • | Hood switch voltage less than 0.05 volts. |
| • | HCM run time greater than 5 seconds. |
Action Taken When the DTC Sets
| • | The IPC displays a hood ajar message. |
| • | The PCM stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp MIL will not illuminate. |
Conditions for Clearing the DTC
| • | A current DTC Last Test Failed clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Diagnostic Aids
Ensure there are no obstructions underhood to prevent the hood from closing securely.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Starting and Charging Schematics Connector End View Reference: Engine Electrical Connector End Views | |||
1 | Did you perform the Engine Electrical Diagnostic System Check? | Go to Step 2 | |
2 |
Does the scan tool display open? | Go to Step 3 | Go to Step 4 |
3 |
Does the hood switch status parameter change state? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 4 |
4 |
Does the scan tool display normal state? | Go to Step 7 | Go to Step 5 |
5 | Test the reference circuit of the hood switch for a open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 6 |
6 | Inspect for poor connections at the harness connector of the HCM . Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 8 |
7 | Inspect for poor connections at the harness connector of the hood switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 9 |
8 |
Important: Always perform the setup procedure for the HCM.
Did you complete the replacement? | Go to Step 10 | -- |
9 | Replace the hood switch. Refer to Hood Primary and Secondary Latch Replacement in Body Front End. Did you complete the replacement? | Go to Step 10 | -- |
10 |
Does the DTC reset? | Go to Step 2 | System OK |
