'98 Explorer EB V8 -- Check Engine Light?

Hi Steven,

A quick google search found this at

This has been a tricky problem for most mechanics and exhaust shops, When diagnosing the problem with a scan tool. The code that comes up for an inefficient Catalytic Converter is a PO420. This is an indication that the Catalytic Converter is not doing its job properly but we have found that this code could also occur if the Oxygen Sensor (O2 Sensor) or sensors become faulty or lazy, We have also found that on the Jeep Cherokee, Subaru Outback, Ford Explorer and Honda Accord, the factory tolerances that set off the check engine light are very tight and an engine that has carbon buildup in the combustion chamber will bring up the cylinder head temperature which in turn brings up the Oxides of Nitrogen (NOX) and will set the light off. In these cases we recommend a product on the market that has been working well to cut down on the carbon build up and will reduce the dreaded check engine light and PO420 code. The product is called BG44K- Total Deposit Control Fuel Additive and can be purchased from us at our product link. A good rule of thumb here is to make sure all components that we have mentioned here have been checked before the Catalytic Converter is replaced. There is nothing worse than spending hard earned money on a Catalytic Converter and find out that the check engine light problem still exists.

The code readers are just a first step in diagnosing the problem. I also have a 98 with 96K miles. A few months ago the check engine light came on with the same code. Diagnoses showed that one of the O2 sensors on an exhaust down tube was flaky, ie, the voltage coming out of it was not moving. A new one was screwed in and the check engine light has not come on since. Mark