P0496 Diagnostic and Fix for 2005 GMC Yukon Denali 6.0L V8 Engine
I recently encountered the P0496 diagnostic trouble code (DTC) in my 2005 GMC Yukon Denali with a 6.0L engine. The issue first appeared shortly after I began towing a utility trailer. After completing the towing task, the Malfunction Indicator Lamp (MIL) turned off after a few starts. However, it has now remained illuminated continuously—whether or not I am towing. Using an Innova OBD2 scanner, I confirmed that P0496 is both currently stored and pending. Additionally, there are two pending DTCs: P0455 and P0496. This suggests a potential issue with the evaporative emission system, particularly related to vacuum control during non-purge cycles. I'm seeking advice on possible root causes and troubleshooting steps.
The P0496 code typically indicates a vacuum (purge) leak detected during non-purge conditions—this could point to a faulty purge valve or carbon buildup in the valve seal. Overfueling, especially when continuing to fuel after the engine has stopped pumping, can lead to carbon deposits that prevent proper sealing. It's recommended to inspect the purge valve for integrity and ensure it is not obstructed by carbon build-up. For more details, refer to OBD-Codes.com: https://www.obd-codes.com/p0496