I scanned my car and got two errors:
p0300 - Random Cylinder misfire
p0420- Catalyst running below efficiency (Bank1)

I was wondering what steps should i take? I have a slightly burnt wire I am replacing as soon as i get a chance, I believe that may be the misfire problem because i got all new taylor wires and tr-55s. I am gonna check all the wires to make sure

Do you think the misfire is leading to the catalyst error? Also, is the catalyst error the one form a loose gas cap?

Is it possible that there is no misfire and there is just a bad sensor giving the error?

My car runs very strong and if the light wasn't on, i wouldn't suspect it.

Im gonna check all the plugs and wires, anything else i should do?

 

The code is for low cat convertor efficiency on Bank 1. Either the convertor or the after-cat O2 sensor is faulty. Switch the after-cat sensors from side to side. If the problem stays on Bank 1, its a convertor or wiring problem. If the problem follows the sensor to the passenger side, its a sensor problem.

P0420 has absolutely nothing to do with a loose gas cap. It also would not show up as any loss of power.... its simply telling you one of your cats may not be working.

If you know you have a burned (plug???) wire, fix it, then see what happens.

 

Sorry to ressurect an old thread -

but my car threw p0420, and the dealer I took it to replaced the catalytic converter for free. Hopefully they changed the right cat, because about 30 miles after I got the car back, the SES (p0420) came right back on! Argh!

Is it safe to say that the rear o2 on bank 1 is bad? Is there anything else that can set this code?

I'm thinking of just buying 2 o2 simms and being done with it..

 

Could be a faulty sensor or faulty wiring. Swapping the sensors side to side is one way to check the sensor.