EI07238 - Fuel Cap May Not Seal, MIL/SES Light Illuminated with DTC P0442 - Evaporative Emission (EVAP) System Small Leak Detected and/or P0455 - Evaporative Emission (EVAP) System Large Leak Detected

This bulletin is being revised to change the Engineering Contact Information and update the Important and Note Statements. Please discard Corporate Bulletin Number 07-06-04-022E (Section 06 -- Engine/Propulsion System).

Some customers may comment on a Service Engine Soon (SES) Light illuminated on the IP cluster and the fuel cap does not seal or tighten. Technicians may find DTC P0442 and/or P0455 set.

GM Engineering is attempting to determine the root cause for fuel caps not sealing and/or setting codes P0442 or P0455. GM Engineering has a need to obtain information first hand from the dealer technician during diagnosis and before repair. As a result, this information will be used by engineering to "root cause" the customer's concern and develop/validate a field fix. Please follow the instructions below regarding the requested information.

Important: If a vehicle is encountered with the above concern, complete the following steps; making sure all the information is documented on the Repair Order.

1. Verify that the VIN and mileage is accurate.
2. Accurately document the customers concern. If the SES light is illuminated, record the Diagnostic Trouble Codes (DTC) using a Tech 2®.

Important: DO NOT use fuel tank filler pipe/neck test adapters, fuel cap testers or smog machines when trying to root cause the EVAP leak.

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 or 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.

•	If DTC P0442 - Evaporative Emission (EVAP) System Small Leak Detected is stored, proceed to diagnosis DTC P0442 in SI.

•	If DTC P0455 - Evaporative Emission (EVAP) System Large Leak Detected is stored, proceed to diagnosis DTC P0455 in SI.

•	If diagnostics lead to repair other components not related to the fuel tank filler pipe neck or fuel cap, repair accordingly and disregard this bulletin.

3. If the diagnostics lead to a leak at the fuel tank filler pipe neck or the fuel cap area, inspect for the following conditions:

•	Inspect the condition of the fuel cap by looking for small cracks or any damaged components.

•	Inspect the fuel cap seal for distortion or cuts.

•	Inspect the fuel filler neck sealing surface for gouges or dents produced accidentally by a fuel nozzle.

4. Contact the appropriate GM Engineer once the vehicle has been diagnosed and before repairing the vehicle for further instructions.

Contact the appropriate GM Engineer from the list below before repairing the vehicle. GM Engineer Shane Isenhoff may be used as a secondary contact. GM Engineering may visit dealerships near the Southwest Michigan area. In either case, you will receive a response back within 2 hours on what action to take the same day of your call (Eastern Daylight Time).

If you do not receive a response from engineering, then proceed to repair the vehicle.

Important: DO NOT use the labor operation listed below if engineering did not respond.

For vehicles repaired under engineering direction, use: