Code P0135 recurs after an hour?

I have, much to my regret, become "elderly", and given this sensor being fairly difficult to access am intimidated by the thought of attacking it myself. My normal 'trusted' mechanic presumably has already replaced the sensor, and given the failure, says he needs to replace the 'other' sensor, despite the code being P0135. I suppose he didn't do any tests and simply replaced the sensor, since that's usually it. And as a lazy owner, just what I've done in the past, so I don't blame him except for his next step being selling me a different sensor.

Thanks for the excellent detailed trouble-shooting support. Not sure about real-time data from scanner; watched the smog-test 'readiness' parameters during a driving course intended to satisfy them, and they did change, but after celebrating CEL appeared at engine-start a minute later. My not-well-stated post should have said "does this kind of behavior (drive an hour, get new CEL) say anything about likely cause?

I can, of course, look at the state data for that last event (with a bit of guidance).

Thanks again, I'll do my part at the fund-me button.

Off-topic the web site needs to clarify the donation process. I would expect the drop-down box where you specify the beneficiary would include the person who's helping you and lacking that I assumed they intended everything to go into a pool they doled out per some internal process. I should have entered your name?

You are a kind and generous person, dare I say, 'all too rare in these times'. I wish I could tangibly bring a smile to your face in recognition of that.

John

Yeah, keep in touch. We (with wife Susan) live in Glendora. I'm well past retirement, she just past. I was a real rocket scientist; I got to play with the first-stage engines for the Apollo moon rockets, did spacey things after that, generally related to early warning that something nasty was heading our direction. Susan in the same business.

My P0135 problem "resolved" by being intermittent enough to let me get by smog check. It being not a good thing I'll attend to it eventually, or when it becomes more persistent. My bones are a bit creaky so there are a bunch of things on my to-do list.

I'd been using an independent German (?) Mechanic who might try too hard to be frugal with parts; an alternator failed one month in, and iirc there was another part like that. I suppose I need to have a talk with him, but if you know of a good mechanic not too far from here it would be good to have. I own axlines. Org which means [anybody]@axlines. Org gets to me, e.G. "John".

Have a healthy, safe, and happy holiday season (and beyond).

John