NGC

P0456-EVAP SYSTEM SMALL LEAK

For a complete wiring diagram Consult Diagrams/Electrical.

- When Monitored:
With the ignition off, fuel level less than 88%, ambient temperature between 4° C and 43° C (39° F and 109° F).

- Set Condition:
As temperatures change, a vacuum is created in the fuel tank and Evap system. With the Evap system sealed, the PCM monitors the ESM switch. If the ESM switch does not close within a calibrated time, an error is detected by the PCM. One Trip Fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.Initial Inspection and Diagnostic Overview

Diagnostic Test

1. VEHICLE HISTORY AND SERVICE BULLETIN INVESTIGATION
Ignition on, engine not running.
With a scan tool, select View DTCs and record the related Freeze Frame data if any DTC(s) are present.
Whether or not any DTC(s) are Active you will want to check the following items which may assist in repairing the customer's complaint successfully.
Check the vehicle's repair history.
If the vehicle has a repair history that pertains to the customer's current complaint, review the repair.
Inspect the vehicle for any aftermarket accessories that may have been installed incorrectly.
Check for any service bulletin(s) related to the customer's complaint or DTC(s).
If a service bulletin applies, follow the instructions per the service bulletin.
Choose the following scenario that best applies.

The service bulletin repaired the customer's complaint.

- Testing complete.

A DTC is present, no service bulletins apply, or the service bulletin didn't repair the customer's complaint.

- Go to 2

2. EVAP SYSTEM INSPECTION
Inspect the Evap System for any of the following conditions:
- Holes or cracks
- Loose seal points
- Damaged or missing components
- Incorrect routing of hoses and tubes
- Loose or missing fuel cap
- Damaged or missing fuel cap seal
- Improper installation of the fuel cap
- Damaged locking tabs on the fuel cap and/or filler tube
- Damaged seal points on the fuel cap and/or filler tube
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test. Powertrain Verification Test

No

- Go to 3

3. EVAP PURGE SOLENOID
Disconnect the purge lines at the Evap Purge Solenoid.
Using a hand vacuum pump, apply 10 in of Hg on vacuum to the "CAN" side of the Evap Purge Solenoid.

NOTE: The solenoid should hold vacuum for a minimum of 15 seconds.

Turn the ignition on.
With the scan tool, actuate the Evap Purge Solenoid to the ON position.

NOTE: The vacuum should drop when the solenoid is actuated.

Does the solenoid function as described above?

Yes

- Go to 4

No

- Replace the Evap Purge Solenoid.
- Perform the PCM Verification Test. Powertrain Verification Test

4. EVAP PURGE HOSE/TUBE OBSTRUCTION
Inspect the Evap Purge hose/tube between the Evap Purge Solenoid and the Fuel Tank and between the Fuel Tank and the Evap Purge Canister for proper routing and installation.
Make sure the hoses and tubes are not damaged, kinked, or blocked.
Were any problems found?

Yes

- Repair or replace as necessary.
- Perform the PCM Verification Test. Powertrain Verification Test

No

- Go to 5

5. CHECKING THE EVAPORATIVE SYSTEM FOR LEAKS
Perform the diagnostic procedure for *CHECKING THE EVAPORATIVE SYSTEM FOR LEAKS. Checking the Evaporative System For Leaks
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test. Powertrain Verification Test

No

- Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. Checking For An Intermittent DTC