Hello all, I just purchased a 2002 SS with 14000 original miles. Can anyone tell me if these trouble code numbers 172, 175 and 420 have anything to due with each other? I know that the code 420 means that the catalyst system efficiency is working below threshold for bank 1 (I am not sure which side bank 1 is). Code 172 is system to rich bank 1 and code 175 is system to rich bank 2. I would appreciate any information anyone can provide me on these codes before I take the car to my local dealer. Thank you all.

 

those are all O2 sensor codes, so yeah they are related. The catalyst efficiency code is bascially a failed check of a catalytic converter (bank1=driver side) If this doesn't go away, just replace the O2 sensor with a simulator (switches 0.9V or so to 0V and back with a 3.3 second period or so - you can make out of a 555 timer and just use the voltage drop across a diode as the output)

I imagine this thing has some mods done. No doubt large volume injectors, a cam, or exhaust system, etc. My hunch is, someone threw in some parts and never bother to have the ECM reprogrammed to use them. It is possible both O2 sensors failed, but unlikely. I would bet you need to find a speed shop that can put the car on a dyno and reprogram the fuel and timing maps.