Diagnostic Tips/Recommendations When Performing Evaporative Emission (EVAP) System Leak Tests for Diagnostic Trouble Code (DTC) P0442 and/or P0455. Chevrolet Express 2009

Subject:

Diagnostic Tips/Recommendations When Performing Evaporative Emission (EVAP) System Leak Tests for Diagnostic Trouble Code (DTC) P0442 and/or P0455

Models:

2007-2009 Chevrolet Express

2007-2009 GMC Savana

Do This	Don’t Do This
Use the EVAP service port.	DO NOT use fuel tank filler pipe/neck test adapters.

GM Engineering has determined that a significant percentage of fuel caps are being replaced unnecessarily due to test adapters.

The use of GE-41415-50A - Fuel Tank Cap Adapter as shown from the J-41413-300 kit does not test the seal on the gas cap to the fuel filler pipe/neck. A fuel cap seated on any one of these test adapters often show a large amount of smoke pouring out between the cap and the adapter, even though the cap may seal with no leakage at the fuel tank filler pipe. This same condition may occur when using other emissions fuel cap testers (smog machines, aftermarket hand held testers, etc.). The following Evaporative Emission (EVAP) system leak test procedure should be used to prevent misdiagnosis of the fuel cap.

EVAP System Leak Test Procedure

Note: Skipping the nitrogen flow-meter test and only using the smoke test may lead to misdiagnosis of the fuel cap seal. The nitrogen flow-meter test on the EVAP system must be allowed to fill for 3 to 5 minutes, somewhat longer on vehicles with large fuel tank capabilities, before evaluating the flow. If the flow indicator drops below the red flag and stays below it during or after the fill period, neither the EVAP system nor the fuel cap is leaking.

•	If DTC P0442 EVAP System Small Leak Detected is set, the condition is intermittent.

•	If DTC P0455 EVAP System Large Leak Detected is set, the condition could be caused by a restriction in the purge path. Follow that portion of the DTC P0455 diagnostic procedure that tests for a restriction.

When diagnosing an EVAP system leak, connect the Evaporative Emissions System Tester (EEST) J 41413-200 to the EVAP service port unless directed to do otherwise by the SI diagnostic procedure. If no service port is available, use the CH-48096 EVAP Service Access Port Tool. The fuel cap must be properly seated on the fuel tank filler pipe/neck when performing the EVAP Smoke Test. Refer to the applicable Evaporative Emission System Diagnosis in SI.

2008 GMC Savana EVAP Service Port Shown (RPO LY2)

When using the J-41413-200 - Evaporative Emission System Tester (EEST) to properly diagnose the fuel cap seal, the nitrogen/smoke hose must be connected to the vehicle using the engine service port (1) located near the purge solenoid. The fuel cap must be properly installed onto the fuel tank filler pipe/neck. For vehicles without a service port, disconnect the purge tube at the quick connector on the EVAP canister side of the purge solenoid valve and install the CH-48096. Then follow the Evaporative Emission System Diagnosis document procedures in SI.

Following these procedures and using the correct tools should help ensure proper diagnosis.