Circuit Description
The DTC P0496 Evaporative Emission (EVAP) System Flow During Non-Purge diagnostic monitors the operation of the EVAP canister purge valve. Ignition voltage is supplied directly to the EVAP canister purge valve solenoid. The powertrain control module (PCM) supplies a ground path to the solenoid control circuit using an internal solid state device called a driver. Each driver has a fault line that is monitored by the PCM. When the PCM commands the solenoid ON, the voltage on the control circuit should be near zero or low. When the diagnostic runs, the PCM closes the purge solenoid and the vent solenoid at the same time, while monitoring fuel tank pressure. Fuel tank pressure should remain constant when both solenoids are closed. If a pressure change is detected that is more than expected, a DTC P0496 will set.
Condition for Running the DTC
| • | DTC P0444, DTC P0445, DTC P0447, DTC P0448, DTC P0451, DTC P0452, DTC P0453 are not set. |
| • | Barometric pressure (BARO) is more than 75 kPa. |
| • | Engine coolant temperature (ECT) is between -8°C to +110°C (18-230°F). |
| • | Intake air temperature (IAT) is between -14°C to +70°C (7-158°F). |
| • | Fuel tank level is between 25-75 percent. |
| • | The engine is running. |
| • | The EVAP canister purge solenoid and vent solenoids are both closed. |
Conditions for Setting the DTC
The pressure in the fuel tank decreases below a specified value when the purge solenoid is OFF.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after 3 consecutively passing trips without a fault present. |
| • | A history DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Perform the scan tool Clear DTC Information function in order to clear the DTC. |
Diagnostic Aids
Check for the following conditions:
| • | Test the operation of the EVAP canister purge valve. Refer to Evaporative Emission Control System Diagnosis . |
| • | An EVAP canister purge valve that leaks or sticks open can cause a DTC P0496 to set. Inspect the operation of the purge valve when the solenoid is hot. |
| • | If a DTC P0496 is intermittent, driving the vehicle under the conditions outlined in the Inspection/Maintenance (I/M) section can verify whether the fault is present. Refer to Inspection/Maintenance (I/M) Complete System Set Procedure . |
An intermittent malfunction may be caused by a fault in the electrical circuit of the EVAP canister purge valve . Inspect the wiring harness and the components for an intermittent condition. Refer to Intermittent Conditions .
If a DTC P0496 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC was first set.
Test Description
The numbers below refer to the step numbers in the diagnostic table.
-
The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
-
This step checks the operation of the EVAP canister purge valve . The duty cycle control of the EVAP canister purge valve is disabled by the PCM until the engine has reached a normal operating temperature of at least 80°C (176°F), there is no RPM indicated, and there are no DTCs set. The output controls can be found on the scan tool under Special Functions.
-
This step determines if the malfunction that caused DTC P0496 to set is still present. Driving the vehicle under these conditions will verify whether the fault is present. After performing the scan tool Clear DTC Information function, the DTC P0496 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If DTC P0496 appears in the Not Ran Since Code Cleared list, the DTC P0496 diagnostic has not yet run. When DTC P0496 does not appear in the Not Ran Since Code Cleared list, the DTC P0496 diagnostic has run. If the MIL is NOT illuminated and there is no Pending DTC Status in DTC Information, the DTC P0496 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||
Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | ||||||
2 |
Is the resistance within the specified range? | 28-36 ohms at 20°C (68°F) | Go to Step 3 | Go to Step 6 | ||||
Does the EVAP canister purge valve pass both inspections? | -- | Go to Step 4 | Go to Step 6 | |||||
4 |
Did you find and correct a condition? | -- | Go to Step 7 | Go to Step 5 | ||||
5 |
Did you find and correct a condition? | -- | Go to Step 7 | Go to Diagnostic Aids | ||||
6 | Replace the EVAP canister purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement . Did you complete the replacement? | -- | Go to Step 7 | -- | ||||
Does the DTC run and pass? | -- | Go to Step 8 | Go to Step 2 | |||||
8 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||
