09-04-2024, 10:10 AM
Just got hit with the "catalyst system efficiency below threshold" code, P0420, on my Grand Cherokee. Anyone else dealt with this? From what I’ve read, it could be the O2 sensors, or worst-case scenario, the catalytic converter needs replacing. Before I go to the shop, any DIY tips to fix this at home? I’m not trying to drop $$$ if I can avoid it!