My '98 es300 has lately been throwing a momentary, intermittent P0135 code. After a cold start, and driving for about 10 miles, or 20-30 minutes, it will light up the CEL. So I've left my OBD reader hooked up while driving, and can reset(clear) it immediately every time. Then 15-30 minutes later, it reappears. So, is this a tell-tell sign of impending permanent failure? Should I just bite the bullet and order a Denso replacement(s)? Should I go ahead and do BOTH upstream sensors? Not looking forward to this particular task, but oh well. Please chime in.

 

Well, 3 weeks later, with no one commenting on my post, I went ahead a ordered the two upstream O2 sensors from Rock Auto. The front one took all of 5 minutes to replace. After jacking up and placing the front wheels on 6" blocks, working from underneath was okay. The rear bank however was much more "fun". I didn't need any special tool(socket) fortunately, a 7/8" combo wrench was fine. The electrical connectors were the hardest part to disconnect/reconnect. No rust or stubborn threads- also fortunately. That took about 30 mins. The only real issue was that afterwards, even with wearing a long sleeve shirt and mechanics gloves, my arms are black & blue and bloody! LOL! Other than that, we'll see if the CEL codes stay absent.

 

What brand sensors did you get?

 

Went with the Densos. $90/pr.