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.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0459 EVAP Purge Solenoid Control Circuit High Voltage
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 ohms. |
| • | 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 . |
| • | 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. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Do you hear or feel a clicking from the EVAP canister purge solenoid valve when the valve is commanded to 50 percent? | Go to Step 3 | Go to Step 4 |
3 |
Does the DTC fail this ignition? | Go to Step 4 | Go to Diagnostic Aids |
4 |
Does the test lamp illuminate? | Go to Step 5 | Go to Step 6 |
5 | Test the control circuit of the EVAP canister purge solenoid valve for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 7 |
6 | Inspect for an intermittent and for a poor connection at the EVAP canister purge solenoid valve. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 8 |
7 | Inspect for an intermittent and for a poor connection at the control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 9 |
8 | Replace the EVAP canister purge solenoid valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement . Did you complete the replacement? | Go to Step 10 | -- |
9 | Replace the engine control module (ECM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 10 | -- |
10 |
Does the DTC run and pass? | Go to Step 11 | Go to Step 2 |
11 | Observe the Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |
