odb II codes

I have recieced an obd II cose of P0420 which is catalyst system efficiency below threshold bank 14. I would like to know what bank 14 is.

99 grand am

Circuit Description
A three-way catalytic (TWC) converter is used in order to control the exhaust emissions of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx). The catalyst within the converter promotes a chemical reaction which oxidizes the HC and the CO that is present in the exhaust gas. This will convert the HC and the CO into a harmless water vapor and a carbon dioxide, and reduces the NOx, converting the NOx into nitrogen. The catalytic converter also has the ability to store oxygen. The Powertrain Control Module (PCM) has the capability to monitor this process by using a heated oxygen sensor (HO2S) which is in the exhaust stream past the three-way catalytic converter. The HO2S produces an output signal which indicates the oxygen storage capacity of the catalyst. This in turn indicates the catalysts ability to convert the exhaust emissions effectively. The PCM monitors the catalyst efficiency by first allowing the catalyst to heat up, waiting for a stabilization period while the engine is idling. Then, the PCM adds and removes the fuel while monitoring the reaction of the HO2S. When the catalyst is functioning properly, the HO2S 2 response to the extra fuel is slow compared to the O2S 1. When the HO2S 2 response is close to that of the O2S 1, the oxygen storage capability or efficiency of the catalyst is considered to be bad and the MIL will illuminate.

Conditions for Setting the DTC
The HO2S 2 response is too quick.

basically is telling you something went wrong with your catalytic converter....probably either the o2 sensor needs replacement...or maybe the cat...

thanks for your response my 99 grand am failed and emission test and had to it repaired didn't think the cat should go bad after only 5 years not sure if that is typical or not.

i would take a look at the H02S(the sensor after the cat)...that may be going bad as well....or perhaps the first O2S may be going bad....i wouldnt just replace the cat...cuz that can be expensive...

If the O2 sensor is bad then replace it but you need to find out what caused the O2 to go bad.

I would try to clean the EGR and EGR passage ways to the Intake and from the Exhaust.

I would use a higher grade fuel for now and put water remover (ISO-HEET) bottle and a fuel injector cleaner.

Check your Ignition Coil tower tips for corrosion and clean it with sandpaper and then coat it with di-electric grease.