Your Suzuki Grand Vitara (assuming it's V6 engine) has 3 catalytic converters. There is one for the left bank of cylinders, one for the engine's right bank, and a third CAT (main catalytic converter) that is located beneath your vehicles chassis and joins both bank 1 and bank 2 converters together. Bank 2 is the passenger side of your vehicle.
Your Grand Vitara GV v6 has 4 oxygen sensors; 2 on each exhaust pipe that comes directly out of each exhaust manifold on either side of engine. On both bank 1 and bank 2, one oxygen sensor is located above (upstream) of the first catalytic converter, one is located below (downstream) of the CAT. The upstream sensor is considered Oxygen Sensor O2 (1) and the downstream oxygen sensor is O2 (2). The oxygen sensors measure the amount of oxygen in the exhaust before and after the catalytic converters. When they don't see much change from the before sensor before and after the catalytic converter the ECU sets a fault code P0430.
In this specific case, given the fact that your Suzuki had trouble in the past which required replacement of one CAT, it is reasonable to expect that the second CAT (in this case Bank 2) has become defective as well. You should consider inspecting the main CAT as well. The sure way of knowing the condition of any of your vehicle's catalytic converters is by conducting a "CAT Intrusive Test". This test (conducted at a smog station) will measure your Suzuki's exhaust sample before the CAT and after the CAT. This will give a clear indication of the CAT's efficiency.
