My check engine has come back on. I had it at the dealer last week and the error message was P0420 Catalyst System Inefficiency. They claimed this was caused by misfiring from last time when fuel got into converter not completely burned. I bought the car (used - 87K miles) at the beginning of the month and two days later the check engine light and the trac control light were on and it ran rough. The diagnosis at that time was that a spark plug was fouled due to the steam cleaning of the engine. After replacing the plug, everything ran fine.
Now if I am to believe them, this problem should go away. However, how can I reset the check engine light myself, without taking it into the shop?
Thanks.
97 LS400 (want to be) Happy Owner