No go on 02 sensor DIY, and what I've learned

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Jul 10, 2022
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I was unable to do my Lexus V8, in the driveway with car jacked up.

I found a pic online so I would know what I was looking at--this would be from the pass side which I was primarily focused upon due to a P0051:

IMG-8398.jpg

The sensor is angled down, and in, so now imagine trying to deal with it considering a hand can't really get there. I believe the connector is undone using a hook since again a hand really can't reach it. I managed to get a offset 02 sensor tool on the sensor, but it was really difficult to get it positioned correctly, and my ratchet head kept swiveling. What a mess. When I did manage to get it on properly, it wouldn't budge so I rounded a corner or two. Also, the straw of the WD40 penetrant didn't come anywhere close to the sensor and there was a heat shield. I let it run down.

At any rate, while I had the underbelly pan off, I noticed the white wire behind the car's or engine's plug, to be twisted together, as if someone spliced it. You know if this were home electrical, it would have a wire nut. I've had the car 6 years, it's a 2006, so it wasn't under my ownership (never got a check engine until now).

Off I go to the indie. I gave them Denso 02 sensors, cost me $52 for the pass side, $42 for the driver (the Lexus parts are $233 and $174 respectively--OUCH). Driver side has a shorter wire.

With my car on the lift talking to the owner and tech, I got a tip, because I said wow look at that--I was not able to get it out (easier to visualize when car is on lift).

Owner said, no, you'd have a very hard time trying to do that from the ground.

I say, also, not only could I not reach the sensor with my WD40, but I don't understand, how would it even penetrate if I could (there's a crush washer, I mean that's the equivalent to me of an oil drain plug washer--to prevent any seepage). He said it wouldn't, you're right. You have to carefully crack it just a little, then spray, then wait. AH!!! Now I get it--just like when I installed a trailer hitch on my wife's 10 y.o. SUV. All the pre-drilled threads were severely rusted--had to be very careful in trying to spray, then clean the threads, and to work the hitch bolts in and out, prior to chasing the threads....

Now came the bad news from the desk person. After replacing both sensors, the check engine was still there. They needed to repair the wiring. Here's a pic that I took last weekend--it was here and also further up:

IMG-9240.JPG


What you're looking at is on the right side, that's behind the car's plug to the 02 sensor. To the left, that's going somewhere up to a module etc., maybe a relay, but the engine side. See the white wire? It's a little damp from slight seepage from the valve covers (the car is 17 so eventually gonna need gaskets done, no top offs between oil changes needed).

In the end, I was out the door at $300--the wire repair cost another $120. I actually don't mind paying in these cases where I failed on my own. I say at least I tried, and when in combination with a competent indie, I learned. Also, can you imagine how much it would have been at the dealer? imho the wire problem would send the price up exponentially. So even though I prematurely replaced the 2 upstream sensors, at $52 and $42 and $180 labor, it's OK.

A very good feeling--no MIL came back, and I drove about 60 miles so far. Every I/M category is ready, except EVAP. That seems to always be the category that takes the longest. It probably requires a cold start. My wife's GM takes 800-1000 miles if you can believe that (UGH).

btw the downstream sensors are completely accessible from underneath. I would attempt, but very good chance they don't budge. Also, the wiring goes through the floor and into the center console where they plug in. I saw on YouTube where someone sliced the carpet open--I'd double check that one lol and hope I never need to address them...

edit: I just found something--the Toyota part pricing is reversed--the driver side with the short wire, costs more. Whereas the Denso part, the pass side costs more. So, is it possible then, to buy 2 pass side Toyota branded OE sensors, and use them on both sides, or, are the plugs different? I would think they're the same, so one would just have excess wire and save money? lol But I think Denso or Bosch are better choices. In the Japanese car world, I have a very hard time researching if a part is OEM or aftermarket--whereas with German it seems totally transparent. My hunch? My Denso parts are aftermarket, not OEM, because they are made in USA. But that's not the only factor--my wife's GM SUV has a OE alternator made by Denso in the USA...haha

Here's what I mean, found this pic online showing the Toyota part is made in Japan



sens7.JPG
 
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Joined
Oct 1, 2010
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Even vaunted Toyota makes cars that have maintenance nightmares. I have replaced O2 sensors on my 2002 Camaro, and it was fairly easy. On the other hand, replacing the alternator was difficult. Have to jack up the car to get access, and one of the electrical connectors is inaccessible for the purpose of disconnecting it. I've done that particular job twice, made easier the second time by lengthening wires so I could pull the alternator down to get access to the offending connector.
 
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I tried to replace the pre-cat sensors on my old 2001 BMW 330Ci. I was doing it at the auto hobby shop at the local army base (I'm retired Navy). Tried soaking with penetrating oil, a breaker bar, having the shop manager to try (big guy). In the end I took the car and the sensors to the my trusty BMW indie shop. Cost me $300 to get them sukkers out and replaced. Heat did the trick.
 
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Thanks for sharing - it probably will help others that are facing this repair.

Your thread almost sounds like you are asking for affirmation that it was o.k. to spend a "bunch" of money for the repair. We DIYers get so conditioned about how much money we save with self repairs that we (I) sometimes feel guilty for having to use and pay a shop. I say bull hockey to that. Everything doesn't go as planned, even for the pros. It's smart to pay experienced, better equipped technicians to get the job done. You are not "out" anything. You have a functioning car with no CEL's now, along with peace of mind.
 
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John105

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btw update, I started the car, did some errands, and when I came back, scanned. The I/M is now a yes, and the EVAP was ready. Total mileage couldn't be more than 85 miles since it was reset, and no more than 10 miles on Saturday. Only people here would understand how satisfying it is, to know the car is ready for emissions testing and legit. Many people just don't keep cars long enough to have emissions problems. And I have a close friend who always turns it into politics saying they don't test emissions in FLA. I say yes, I get it, but if this P0051 happened and I live in FLA, I still want to fix it.

Thanks guys hopefully you don't get the check engine but if you do you can solve it...

If you want to read the crazy GM EVAP procedure....

 
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Thanks for sharing - it probably will help others that are facing this repair.

Your thread almost sounds like you are asking for affirmation that it was o.k. to spend a "bunch" of money for the repair. We DIYers get so conditioned about how much money we save with self repairs that we (I) sometimes feel guilty for having to use and pay a shop. I say bull hockey to that. Everything doesn't go as planned, even for the pros. It's smart to pay experienced, better equipped technicians to get the job done. You are not "out" anything. You have a functioning car with no CEL's now, along with peace of mind.
Very true. Sometimes a problem comes up and it's a first for us diy guys to figure out. The shop guys deal with it every week and already know how to deal with most hiccups.
 
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I tried to replace the pre-cat sensors on my old 2001 BMW 330Ci. I was doing it at the auto hobby shop at the local army base (I'm retired Navy). Tried soaking with penetrating oil, a breaker bar, having the shop manager to try (big guy). In the end I took the car and the sensors to the my trusty BMW indie shop. Cost me $300 to get them sukkers out and replaced. Heat did the trick.
Imagine doing the post-cat o2 sensors..
 
Joined
Jul 13, 2003
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Tracy, CA
Even vaunted Toyota makes cars that have maintenance nightmares. I have replaced O2 sensors on my 2002 Camaro, and it was fairly easy. On the other hand, replacing the alternator was difficult. Have to jack up the car to get access, and one of the electrical connectors is inaccessible for the purpose of disconnecting it. I've done that particular job twice, made easier the second time by lengthening wires so I could pull the alternator down to get access to the offending connector.
To remove the downstream O2 sensors in the LS400, you have to take apart the interior to get to the connectors,
 

John105

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Imagine doing the post-cat o2 sensors..
What do they look like on that 330Ci? That was actually my dream car at the time, the E46 coupe. As my story goes, I couldn't get my financial ducks in a row and timing lead to the 2007 335i coupe. No idea what my 02's look like on it, hope I never find out hahahahahahaha as everything is tight. I did manage to do the ABS/DSC hydro job on it but I took my time, 4 months lol. And when the Lexus was down these past few weeks, I got to drive the 335i daily and it was a pleasure. I really like to have cars be diffferent so we have one from the USA, one from Japan, and one from Germany. Again good feeling to know my emissions is legit and problem is solved, even though it needed a trip to the indie.
 

John105

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In the end, the car passed safety and emissions, and because I was 4 days late, my new stickers have month 11, instead of 10 (in PA you can inspect an October expiration in Aug, Sep, Oct, but if your stickers expired, then one for the current month are applied--it's wonky, imho there's enough technology to generate a violation but I guess that's just mean lol). I actually don't think anyone cares in PA. But it's amazing how much disappointment a check engine light can bring. The reason is I feel it's emissions related, repairs can get expensive, and that's what brought about the downfall of my 1998 purchased new car, in 2016. When a car is that old, it's questionable if one is willing to invest say $1000+ to correct emissions....in this case I escaped with about $390 out of pocket, and in reality, I have new upstream sensors and the problem was really a broken wire. But knock on wood from what I've read it stands to reason upstream goes bad before downstream, as downstream is cleaner post cats?
 
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