Hi

Hope this helps.
:-)

DTC P0420: Catalytic System Efficiency Below Threshold. Basically it's
saying the catalytic converter is not working properly. But before we
go and replace it, we need to check it.

First clear all the codes from the Powertrain Control Module (PCM)
thusly.

Turn the ignition switch OFF , and remove the No.13 CLOCK BACKUP fuse
(7.5 A) (A) from the passenger's under-dash fuse/relay box (B) for 10
seconds.

Now, start the engine and hold the engine at 3,000 rpm with no load, in
Park or neutral, until the radiator fan comes on.

Test-drive 40 to 55 mph for approximately two minutes. Then decelerate
for at least 3 seconds with the throttle completely closed. Then reduce
the vehicle speed to 35 mph. If the light comes back on, you will need
to replace the catalytic converter.

Frank
www.NGKPartFinder.com - Best site to find all NGK products for your
vehicle.