Results for "p0420"

Opened my wallet for a new catalytic converter, cleaned the MAF sensor, checked every vacuum line, and swapped the fuel filter on my 2014 Ford V10 motorhome — still getting P0420 codes and intermittent surging. Some days it runs absolutely perfect, smooth acceleration and no codes. Other days, especially during acceleration, I get this annoying surging that makes driving unpleasant, and that's when the P0420 code shows up on my scanner.

I've been methodically working through potential causes and have replaced quite a bit already: new MAF sensor, both upstream and downstream O2 sensors, checked fuel pressure (it's good), tested plugs and coils, cleaned the throttle body thoroughly, and even replaced the right side exhaust manifold gasket after noticing some seepage there. Despite all this work, I'm still getting the same P0420 code and surging, and my scan tool consistently points to issues on the right bank.

What's really puzzling me is the connection between the surging and the P0420 code - they seem to occur together. Could there be something I'm missing with the exhaust system that would cause both symptoms? I've already addressed the right side manifold, but I'm wondering if there's more to this V10 exhaust system that I should be checking. …more