P0421 : Warm up catalyst efficiency below thresh hold bank 1
P0421 code = Warm up catalyst efficiency below threshold, Bank 1
Trouble code P0421 means:Warm up catalyst system efficiency below threshold
Trouble code P0421 means: Catalyst Efficiency Below Normal (Bank 1)
Trouble code P0421 means:Warm up catalyst system efficiency below threshold
P0421 : Warm up catalyst efficiency below thresh hold bank 1
Trouble code P0421 means: Catalyst Efficiency Below Normal (Bank 1)
Trouble code P0421 means: Catalyst Efficiency Below Normal (Bank 1)
Trouble code P0421 means: Catalyst Efficiency Below Normal (Bank 1)
When this code come out may be haven no enough warm up on the catalyst is efficienecy the vehicle has an exhaust leak
Passenger side and after the catalytic converter O2 sensor.
Trouble code P0420 means: Warmup Catalyst System Efficiency Low (Bank 1)
I believe 0421 is a catalytic converter inefficiency code which is usually caused by a bad o2 sensor or a bad catalytic converter, but I have also seen fouled plugs and exhaust leaks cause this code.