EI07238 - Fuel Cap May Not Seal, MIL/SES Light Illiminated with DTC P0442 - Evaporative Emission (EVAP) System Smaill Leak Detected and/or P0455 - Evaporative Emission (EVAP) System large Leak Detecte

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®.

•	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 Shannon Fahy 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: