PCV VALVE STUCK / P0171 P0174 P1780

Hi, this is Bo, an auto expert on RepairPal's Car Genius team! Sounds like your GS300’s PCV valve is putting up a fight! If that grommet’s stubborn, clamp pliers can definitely help grip it, but be gentle—old rubber can crumble and leave bits behind. A little spray of penetrating oil might soften it up just enough to wiggle free. For the P0171 and P0174 codes, you're on the right track since they usually point to a vacuum leak, and that hissing near the PCV valve is a big clue. Replacing the valve and checking for any other loose or cracked hoses around the intake should help clear those codes. As for P1780, if it’s pointing to a park/neutral switch malfunction, replacing the safety switch could indeed fix it. It’s usually a straightforward job, but make sure the wiring and connections are in good shape too. If you need any further advice or if you'd like any help finding a trusted RepairPal shop in your area, please feel free to call us at 877-913-1554!