OBD code P0421, 1999 Mazda Protege

sbhunia

My 1999 Mazda Protege ES 1.8L engine, manual transmission with 127430 miles is throwing OBD code P0421 (Warm up Catalyst Efficiency Below Threshold). I used torque app to read O2 sensor reading. The car was parked overnight and today I start it and took readings. The reading graphs are given below. Could anyone suggest me about the problem or what else should I track to get an idea bout which part is faulty. Should I use any combustion chamber cleaner?

2 minutes after starting the car in neutral gear:

after driving for 3 minutes In second gear while driving around 20mph

after driving for 10 minutes