Savana 3500 V8-4.8L (2009)
Fuel Filler Cap: Technical Service Bulletins
Emissions - Diagnostic Tips For DTC's P0443/P0455
INFORMATION
Bulletin No.: 08-06-04-044
Date: September 22, 2008
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
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)
