P0459

DTC P0459

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 canister purge solenoid valve is used to control the flow of fuel vapor from the EVAP canister to the intake manifold. The engine control module (ECM) controls the EVAP canister solenoid valve by supplying it ground whenever the EVAP system is in purge mode. Fuel vapors can be purged anytime the ECM is in Closed Loop and the vehicle is not in deceleration. When the valve is commanded OFF (circuit not grounded), the voltage level at the ECM should be high (ignition voltage). When the driver is commanded ON (circuit grounded), the voltage level at the ECM should be low. The ECM EVAP canister purge solenoid valve feedback circuit uses a pull-up voltage (2.6-4.6 volts), which allows the ECM to individually differentiate between an Open, short to ground or short to voltage. DTC P0459 will set if the ECM detects a higher than normal feedback voltage when EVAP canister purge solenoid valve is commanded ON with engine cranking/running.

CONDITIONS FOR RUNNING THE DTC
- The engine speed is more than 40 RPM.
- The battery is between 7.5-17.3 volts.
- DTC P0459 runs continuously once the above conditions have been met.

CONDITIONS FOR SETTING THE DTC
The control module detects the EVAP canister purge solenoid valve feedback voltage is greater than 4.6 volts when EVAP canister purge solenoid valve is commanded ON, and the condition exists for longer than 0.5 seconds.

DIAGNOSTIC AIDS
- EVAP canister purge solenoid valve resistance is 16-25 ohm.
- To locate an intermittent problem, command EVAP canister purge solenoid valve ON at 70 percent duty cycle with ignition ON, and the engine OFF, with a scan tool. Wiggling wires while listening for the EVAP canister purge solenoid valve to stop clicking, may locate a shorted valve or the area where a short to voltage in the wiring may exist.
- For intermittent conditions refer to Intermittent Conditions. Intermittent Conditions
- The EVAP canister purge solenoid valve is pulse width modulated (PWM). An audible clicking should be heard when the EVAP canister purge solenoid valve is commanded to 50 percent and should stop when the EVAP canister purge solenoid valve is commanded to 0 percent. The rate at which the valve cycles should increase as the commanded state is increased and decreased as the commanded state is decreased. Repeat the commands as necessary.

TEST

Steps 1-11: