GMC Sonoma Flashing CEL & Stalling, EVAP System Alert

Had similar symptoms on a 2018 GMC Canyon. The EVAP system leak detection revealed multiple issues, with the activated charcoal filter being completely clogged. The fuel tank ventilation was compromised, causing poor air flow and irregular fuel pressure. Main symptoms matched: check engine light and stalling at idle. The clogged charcoal filter disrupted the entire emission control system, leading to improper fuel-air mixture and engine performance issues. The repair required: Complete EVAP system diagnostic, Replacement of activated charcoal filter, Testing of all connected vapor lines, System pressure test to confirm repair This was a serious issue that needed immediate attention, as it affected both fuel efficiency and emissions. Leaving it unfixed risks damage to other engine components and increased fuel consumption. Recommend getting a proper diagnostic scan first. The scanner should show specific EVAP-related trouble codes. This helps pinpoint whether its truly the charcoal filter or possibly other components in the emission control system. The repair itself requires specific knowledge of evaporative emission systems. A certified technician with experience in EVAP system diagnostics would be the best choice for this repair.

Thanks for sharing your experience. I had nearly identical issues when my purge valve failed last year. The pressure sensor readings were all over the place, leading to those exact symptoms, flashing CEL and rough idle. Did you remember roughly what the total repair cost? Also curious if you have encountered any similar emission control problems since getting it fixed? The EVAP diagnosis and repairs can vary quite a bit in price, but having a ballpark figure helps others gauge if they are getting a fair quote. Plus its good to know if the fix actually held up long-term.

Just got the final bill last week, it came to 275 Euro for replacing the defective activated charcoal filter. The EVAP system leak that caused all those issues is completely fixed now. The pressure sensor readings have stayed stable and the fuel tank ventilation is working perfectly. After the repair, I have not seen any check engine lights or emission control problems. The idle is smooth now and fuel efficiency has actually improved. The system failure codes have not returned, which confirms the leak detection system is functioning as it should. I would say its worth the investment since a compromised EVAP system can lead to more expensive repairs if left unchecked. The repair shop did a thorough job testing all components of the emission control system to ensure there were no additional issues. Getting the complete diagnostic definitely helped identify the exact problem. Much better than just throwing parts at it and hoping for the best.

Thanks everyone for the input. I finally got my car checked at a new repair shop yesterday. The technician found that the purge valve was stuck open, causing the erratic air flow and engine stalling. The diagnostic scan confirmed multiple EVAP system codes. Total repair cost was 195 Euro which included: Full EVAP system diagnostic, Purge valve replacement, System pressure testing The emission control system is working perfectly now. No more check engine light and the idle is smooth. The fuel efficiency has improved noticeably too. The new shop did a thorough job explaining the issue and showing me the faulty parts. Much better experience than my last mechanic who just kept clearing the codes without fixing the actual problem. Glad I asked here first and learned what to look for. The EVAP system issues seem pretty common with these models.