The evaporative emission (EVAP) system is used to store fuel vapors as to reduce the amount of unburned fuel from escaping into the atmosphere. The function of the EVAP vent solenoid is solely for EVAP leak diagnostics. Outside air flows around the normally open valve, except during portions of the EVAP diagnostics, through the EVAP canister to the fuel tank. This allows the fuel tank to be at atmospheric pressure, around 101 kPa. The powertrain control module (PCM) controls the EVAP vent solenoid by controlling an internal driver that pulls the solenoid circuit to ground. The EVAP vent solenoid circuit is monitored for low and high voltage faults. DTC P0448 sets when the EVAP vent solenoid is commanded ON and the feedback voltage at the PCM is high.
DTC Parameters
DTC P0448 will set if EVAP vent solenoid feedback voltage is greater than 1.25 volts with EVAP vent solenoid commanded ON when:
| • | The condition exists for longer than 0.5 seconds. |
| • | The engine is running. |
DTC P0448 diagnostic runs continuously with engine running and EVAP vent solenoid commanded ON.
DTC P0448 is a type D DTC.
Diagnostic Aids
To locate an intermittent problem, use a scan tool to command the EVAP VENT SOLENOID ON, while monitoring the EVAP VENT - HIGH VOLT test. When a fault, short to voltage or shorted solenoid exists, the scan tool will display TEST FAIL.
The test will fail only when the device is being commanded ON and the voltage at the PCM is high. The test updates every 100 ms whenever the ignition is turned ON and the device is being commanded ON via the scan tool or PCM.
The EVAP vent solenoid resistance is 15-35 ohms.
