Quote:
Originally Posted by Jim H
Well, hold on, not so fast. I had an "exhaust catalyst efficiency below threshold" type of problem several times, but it was never the cat... Bad spark plugs and 'leaky' spark plug wires produced this code twice. ANY regular misfire can overload the cat just enough to trigger this code. In my case, new plugs made it go away within 8-10 engine start-stop cycles. I came back, and a bad wire made it go away again...
Before you drop $900, be SURE it's the cat!  |
I had the P0420 code shortly after the coil pack failed on my Miata. It was, unfortunately and expensively, the cat.
A good scanner can readout the voltage outputs from the 2 O2 sensors in real time to help identify the true cause of the code.