Questions and Answers

Honda Accord DTC P0420 Q. I keep getting the codes P0420 on my 1998 Honda Accord 5 speed 2.3 liter. Could you possibly tell me what could be the cause? Thank you...

A. 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.