The auto cabin air exchange function in my 04 LS430 UL w/PCS now always stay on auto/interior mode and dose not go to auto/exterior mode anymore. I notice this problem about 2 months ago. When it still function, it stay on auto/interior or auto/exterior by itself depend on any smoky cars in front of you or not. I did turn the smog senor to "HIGH" and "LOW" from the center control penal but this did not help. My questions are:
1. I had my AC filter changed 12/2008. Is this problem related to the A/C filter? (I also had my air filter changed one month ago.)
2. Is the smog sensor broken? Dose any one know how to located and change the smog sensor?
3. Is this could be related to the photocatalyst filter in the trunk air purifier? Dose any one know where to buy this special filter?
4. Or any solution for this auto air exchange problem?

Thanks!


2004 LS430 UL W/PCS silver me/Eru 55,000 miles