For 1990-2009 cars

### Circuit Description

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 EVAP vent solenoid is solely for EVAP leak diagnostics. Outside air flows around the normally open valve, except during portions of the EVAP diagnostic test, through the EVAP canister to the fuel tank. This allows the fuel tank to be at atmospheric pressure, around 101 kPa. The ECM controls the solenoid by supplying it ground whenever the EVAP system is not venting, during the EVAP leak diagnostic test. When the solenoid is commanded OFF, the circuit not grounded, the voltage level at the ECM should be high, ignition voltage. When the solenoid is commanded ON, the circuit grounded, the voltage level at the ECM should be low. The ECM EVAP vent solenoid feedback circuit uses a pull-up voltage, 4.6-6.6 volts, which allows the ECM to individually differentiate between an open, short to ground, or short to voltage. DTC P0448 will set if the ECM detects higher than normal feedback voltage when the EVAP vent solenoid is commanded ON with the engine running.

### Conditions for Setting the DTC

DTC P0448 will set if EVAP vent solenoid feedback voltage is greater than 6.6 volts when the EVAP vent solenoid is commanded ON when:

• | The condition exists for longer than 0.5 seconds.

• | The engine speed is greater than 40 RPM.

• | The battery is between 7.5-15 volts.

DTC P0448 diagnostic runs continuously once the above conditions have been met.

DTC P0448 is a type B DTC.

### Diagnostic Aids

To locate an intermittent problem, use the scan tool to command EVAP VENT SOLENOID ON and OFF with the ignition ON and the engine OFF. Wiggling the wires while listening for the EVAP vent solenoid to stop clicking may locate a shorted solenoid or the area where a short to voltage in the wiring may exist.

EVAP vent solenoid resistance is 18-27 ohms.