My 98' Tahoe has 135,000 miles and was wondering if I should change the O2 sensors or leave it be, runs fine gets 12 mpg, but the cats are shot(PO42 & 43 codes)?


Thanks for any replies!!

If you replace the cats, I'd also replace the front two sensors. Bet you will get a boost in mileage afterwards. The rear sensors monitor the cats, I don't think you would need to replace those unless they throw a code.

1997 Tahoe -118K miles

I just replaced front oxygen sensors on mine. I have smog records and both O2 and CO were going up (meaning rich & lean) but still passing california dyno testing.

I just completed trip up to Lake Tahoe from San Jose. Altitude zero to 8500', 500 miles round trip averaged 15.5 mpg. Previous Tahoe trip was 13.7, historically 15.5 on long trips until reaching over 110K miles. The sensors on this rated expected life 100K. I measured resistance to be greater than 10M ohms so I assume they were shot.

O2 sensors on all 3 of my vehicles were shot (no codes on any and all passed smog, all sensors open).

I got all of them at www.thepartsbin.con Front two for Tahoe $44 each Bosch 15703. They shipped Delphi ES10006 (should be ES10011 which is same). Tell they BOSCH and get $10 coupon off www.boschusa.com.