Hi guys,hopefully this forum has the answer, Ive been looking for a couple years now, off and on.
Desc:
99 4runner 3.4 V6 Cal Emission all factory.
have been getting Obd Codes cant recall 1 of the 2, but one is P0420.
It has been happening for over 3 years now.
I notice that it only throws the code if Im driving on a dusty road or in a extreme snow storm, i figure something is sucking in dirty air somewhere.
The band one sensor fails and has to be replaced one a year or close to.
The longest has been a year and a half, Im on my 3rd new sensor, and it threw a code on the bow hunt, dusty road again.
mechanic said MAF sensor was extremely dirty last year and cleaned it, but threw the code last week. ideas. I have never changed anything since I bought it 7 years ago, changed standard, oil, air filter, plugs, wires(non split).
Thanks for any help.

 

Clean air filter? Cleaned the MAF?

Could be something in the intake system causing the problem if it is only when dusty/snowy.

 

x2... I know you say all stock, but as a dummy check, do you have a cone filter, or CAI on it? How about the deckplate mod? Cone filters often don't filter as well as the OEM style filters.

Try replacing your air filter, vacuuming out the airbox real well, and check for leaks in the intake behind the filter.