tferro86

the code p0420 come out when i check my car with the ob2 it says input/turbine speed sensor A circuit Gear Ratio incorrect what is this and how can i fix it

hbboy07

are you sure its for a a speed sensor i think p0420 is a cat code

emergencybm

iTrader: (1)

po420 is cat efficiency below threshold bank 1 if thats the case its your cat or your secondary o2 sensor thats throwing it

h22civic88

Yeah, a P0420 code is a catalyst efficiency below threshold code which is usually an o2 sensor issue....

Davus

Beg to differ, I threw P0420 a few months back, went to muffler shop and got a stock-replacement-high-flow cat welded in, been gone since.

It usually indicates exactly what it says: That the catalytic converter is dead (mine was alllll burnt up after 240K miles!), not necessarily that the oxygen sensor is bad.

h22civic88

I've had plenty of cars come in the shop and it was the o2 sensor, so everyone will encounter differences... I didnt say always, just I've had may fair share that the o2 was bad with that mil showing...

fsjcowboy

My 2001 CRV threw this code after 139K miles. I replaced the cat with a NAPA factory replacement, the primary O2 sensor with a factory replacement, and the secondary O2 sensor with a Walker universal O2 sensor which I had to splice in because it had no plug (universal). After resetting the faults, the MIL continues with the code reading PO420. I suspect the universal sensor because the voltage reads either 0.00v or 1.25v....nothing in between. The voltage for the primary sensor bounces around from .120v to .720v, which I think is normal. I plan to replace the secondary universal sensor with an OE sensor. I'll follow up with my results after the ECM monitors reset .