Help with P0420 code

Hey guys,

My cats were stolen and replaced with aftermarket cats and now I have the P0420 error code. Low catalyst efficiency. O2 sensor cut and replaced. Any ideas on getting the engine light to clear

 

Have you reset the code? It can be done by disconnecting the negative battery terminal for approximately 10 minutes.

 

Ive reset it with a obd scanner but haven't tried the battery route

 

Should be the same difference. Try doing this procedure. It's for an 02 and earlier, but maybe you can force the ECU to read and reset the code by itself. You may need to ensure the plug is fully seated on its connector and hasn't slipped loose somehow, or made contact with the exhaust and damaged the wiring.

Driving Procedure:
Drive the vehicle at a steady speed at or above 25 mph (40 km/h) for at least 50 seconds. Maintain engine speed above 900 rpm.
Stop the vehicle and allow the engine to idle for 40 seconds or more.
Repeat steps 2 & 3 nine (9) more times.

 

Ok haven't looked at the sensor. Installed a guard on my cats

 

Any other ideas? Thinking about an O2 spacer. Or having someone look into computer settings.