hey guys just replaced all four o2 sensors and both flange gasket after each cat on my gs400 to get rid of the nasty p0420 code that comes and goes, in the past week or so ive been getting VSC OFF and CHECK ENGINE light and a p0120 code which is throttle/pedal position sensor malfunction, already ordered a TPS on amazon to fix that code. so can bad TPS causes p0420 code in anyway?

 

very unlikely. Fix the tps and hopefully be done with your CEL

 

well i was thinking the TPS was telling the ECM that i am applying more throttle than i really am. In that case, extra fuel would have been applied in result confuses the o2 sensor.....? maybe

 

check the ventilation hose and intke air hose.

 

how do those 2 cause the a P0420 code?

 

the causes to broken the "cats or O2 sensors" is pobably "fuel too lean". That will defer the system of fuel get the MAF too low but air intake actually entered more by other leaking way.