A/F and O2 sensors

normski2 · January 6, 2017

Been doing a bit of digging to find the relevant info on the air/fuel (A/F) and oxygen (O2) sensors fitted to our vehicles. Essentially, on the is250, there are four to be considered. There are 2 Upstream sensors (Bank 1 Sensor 1 and Bank 2 Sensor 1) and 2 Downstream sensors located after the cats (Bank 1 Sensor 2 and Bank 2 Sensor 2). The engine is a V6 configuration ( sorry to say the proverbial, but needs must) so we have two Banks of three cylinders. Viewed from the front of the car the bank on the left is Bank 1 and the bank on the right is Bank 2.

Found this to help clarify if anybody not sure.

See below at A ... sorry, all went out whack when I uploaded it all!!

The A/F sensors are good, generally speaking, for 80,000 mls or so. Lexus recommend changing between 80 and 100,000 (but they may last longer). The oxygen sensors are very important because they monitor the air/fuel ratios and exhaust of the engine, so if they fail more pollutants can be released into the atmosphere. This can also cause the engine to run into serious problems including a compromised catalytic converter. You may feel erratic acceleration, notice a bit more smoke from the exhaust, smell a petrol odour, notice your mpg start dropping and if one fails completely you'll get light up on the dash with Check VSC warning. Then you'll need to get the codes read to pinpoint the problematic one (assuming it is indeed a O2 sensor).

Here is another bit of info i found which is a TSB from Lexus. This is handy as it relates to all of the Lexus vehicles. This clarifies further the individual sensor locations.

See below at B

I'm just about to do my 2 Upstream sensors (precautionary move .... as I've noticed a tad more smoke and slight smell of fuel, plus I'm on 74,000 mls) as Lexus will want around £650 to fit them and they are not that tricky to do your self. Newbie has done 2 splendid guides on how to do with excellent photos. Denso are not the most helpful to the UK market but the sensors can be sourced from Rockauto in the USA at much cheaper prices. Import Tax is a grey area ... sometimes you get away with it and sometimes not!! Currently, the sensors are £70-90 from Rockauto (may improve, who knows, the Dollar rate is not brill at the mo ... but heck they're still a darned site cheaper!) or anywhere around £240 each in the UK.

http://www.rockauto.com/en/catalog/lexus

Incidentally, while I'm doing these jobs I shall change the PCV valve too (easy to do while doing Bank 2 Sensor 1, having made the space to get at it!!). Again, got that at same time from Rockauto for £5.40 where Lexus want £26. The PCV valve being gummed up can lead to a bit more exhaust smoke.

Out of interest here are Newbie's guides relate to his 2007 model.

Newbies guide for Bank 2 Sensor 1 is within the above post. This is the best place to look as all the photos are present. Unfortunately much has gone awry in the "How To" section after the last forum update .... most pictures have vanished.

If i discover any differences on a 2010 model I'll put up a walk thru with pics. The only thing I've found thus far is that the sensors have a different reference number. Maybe some modifications were made to the facelift version.

The Bank 1 Sensor 2 and Bank 2 Sensor 2 units are tricky'ish to do as they are essentially under the floor and will require lifting of carpets and moving of seats to get at as they the looms pass through the floor of the car via a weather proof grommet to connect into the exhaust pipes.

I hope that info is of use to some of you.

Happy New Year to all and here's hoping 2017 will be a good one for all.

Right, need a cuppa now!!

A

B

normski2 · January 6, 2017

Well, whad'ya know .... just found this over on the US site relating to Sensor 2 replacement!!

http://www.clublexus.com/forums/is-2nd-gen-2006-2013/843618-diy-is350-oygen-sensor-replacement-p0138-bank-1-sensor-2-a.html

normski2 · January 27, 2017

The parts all duly arrived from the US. Very quick turn around by Rockauto... and did not get walloped for any import duty. It's been raining all day so I put the car in the factory when the lads knocked off at 2pm. Started at 2pm and restarted the car at 4:30 pm. Both upstream sensors [Bank 1 sensor 1 and Bank 2 sensor 1] changed, and the PCV valve too. Noobies guide is excellent to follow..... Big thumbs up from me.

Couple of little differences on the facelift version. I'll put up some picks and a walk through soon as. The hardest part of the whole process was loosening the original sensors so they could be removed. By heavens they were right little so and so's. A pipe extender that fits over your socket handle will come in handy. I had sprayed them a few days before with WD40 too! You have so little room to manoeuvre in there. Expect to curse and cuss a bit. The cost was £190 for both sensors, the pcv valve and carriage. I've noticed the parts have gone up over the last couple of weeks as the exchange rate has worsened. Still, better than £600+ charge from Lexus dealership.

Its a no brainer to do the pcv valve while you're doing Bank 2 sensor 1 as you have removed everything that is in your way. My old pcv was certainly not as rattly as the new one...most definitely gummed up a little bit.

On start up the engine was noticeably smoother and quieter. Having parked her outside in the rain it was very obvious that there was pretty much no smoke from the exhaust pipes. And none seen when reversing back up my drive 30 mins later.

Anyway, i'll put up more later.

Happy days

is200 Newbie · January 27, 2017

Simples

More people need to have a go to realise how easy the maintenance of these are.

You should notice a difference in the drive, maybe mpg of you are watching it - need every mile out of it now the petrol prices are rocketing

true blue · January 27, 2017

Great post Normski , collating all the relevant information into a guide to assist practical members ; I will be doing mine when the time comes ,but it is only at 30,000 miles at present. I have done a few in the past and you are correct ,they are tight to unscrew ,I don't rate WD 40 as a penetrating oil I always use plus gas

Dave

normski2 · January 28, 2017

Thanks

Wish I'd had some plus gas then ....damn.

I was a little concerned that I loaded all the relevant tools in the boot! There was little in the factory of help as are a 'woodworking site'.

I knew from my own extensive searches that it would be helpful to have as much info as possible in one post. Hence the amalgamation of sources.

normski2 · January 28, 2017

Changing the sensors and PCV valve on a 2010 is250 Mine is the SEL ML HDD Nav variant.

So the parts duly arrived from the USA via Rockauto in NY. Very speedy service too!!

First thing was to remove the three engine covers and also the main one in the centre. The Battery and components are all removed in the same process as described by Noobies excellent guide. I had copied and printed and laminated the sheets for guidance. That way they will stand up to greasy hands and can be used again if required. Those connectors into the electronics box are right little so and so's to free up. There is a large one on the right and two on the left side as seen in the photo below

The grey one on the left is conventional squeeze and pull off. The other two (as noobie points out) are somewhat different. You will need a short and small (4mm) flat blade screwdriver to prise up the little black tag. They need to come right up before you can start to lift the securing bar. This white bar has to to come up to 90º as shown on the rhs connector in the photo. This partly frees the connector but they are quite a grunt to pull right out ...and you are always thinking to yourself ...go easy don't break anything. I actually used a larger screwdriver to help prise the connector apart from the electronic box. I laid everything out on the floor in order of how it came out to help with reinstatement.

There is a loom wire attached to the tray and that is a bit of a toad to squeeze at too. I found the only way i could do it was by lifting the tray upright and squeezing the tabs with long nosed pliers. I had dosed the sensors bases with WD40 a couple of times and hoped it would soak in. So I figured I'd crack on with the PCV valve first. With all the Battery parts removed you can get at the valve very easily. Squeeze the wire tag and slide it upwards and then gently pull the tube off and push it out of your way under the bulkhead. Its a 19mm spanner job. A tap with a hammer on the end of the spanner had it moving. It's pretty tight though!

That's the new pcv and the old one removed. The part number is that for a 2010 model. Think it covers 08-12 models IIRC. The valve should rattle but mine sounded nothing like the new one. Bit of threadlock and then refit ...simples!!

New pcv fitted (sorry the pic is sideways, it wasn't when I uploaded it)

All connected and pipe and tag secured.

Then it was on with the sensors. For the 2010 model with Denso sensors the Bank 1 Sensor 1 is part no 234 9048, and the Bank 2 Sensor 1 is part no 234 9068. This is different to Noobies and I don't know if his would have worked in my car or not. But this is what Denso and Rockauto indicated for my car year ... so who am I not to listen.

They are nicely packed and are supplied with a little tube of copper grease to apply to the threads and have threadlock pre-applied at the seat of the threads by the compression washer.

This shows the part numbers together with the old sensors. The cables are different lengths. I guess 9048 could be used for both, but 9068 will not fit on Bank 1 ... it's too short by 50mm.

Bank 1 Sensor 1

The 2010 vehicle differs from Noobies in that there is no fuse box to move out of the way on the drivers side. It is pretty restricted access even so! I had purchased a sensor

socket from China beforehand (£3 delivered), and you will need on of these! They are a 22mm fit and are slotted to accommodate the connector wires. There is also a 3/8" square drive at one end to connect, via an adaptor, to my 1/2" drive socket set. I needed two extensions and a universal drive (to get the angle of attack correct) to get clearance above the engine components. There is no room to get any push lower down and you will end up pulverising your fingers. And you are going to need them for the second sensor!!!! It was a hell of a grunt to get the old sensor to move but it only takes 5mm of movement and it's spinning freely by hand. The actual wire connectors are awkward to undo as you are relying on feel. I had an inspection lamp and a mirror on a telescopic handle that proved invaluable in seeing what the heck was going on behind the engine block.

So this is Bank 1 Sensor 1 finished.

Bank 2 Sensor 1

This is a right pig to do ... sorry, but that's the truth! Access is incredibly restricted and your arms and fingers will take a bit of punishment in the process. Perseverance is the ticket!! I had to cobble up an extension to the t-bar to get the leverage right. Then the relief when the thread goes is immense!! There then follows the same PITA trying to get the wire connectors apart ... and then back together after fitting the new sensor.

That's Bank 2 done!

Then put all the tray, electronic unit, plug connectors, tray base, Battery, Battery shroud, cable clip and connect the Battery.

Having turned the ignition 'ON' there followed a brief bit of computer loading on my screen (I have the nav/reversing camera option) then all systems were ready.....Started first time.

Radio stations were all lost ... no biggie really. [There is no radio code to be concerned about]

Clock will need resetting

Window switches did not need re-syncing ... maybe something changed on the facelift variant!

A/C had to be reset to Auto [as it defaults to 'off'] ... at least that's what I have it set at

Cabin temp setting was unaffected as were audio preferences (Bass, Mid, Treble etc)

Navigator cursor defaults to showing North Which was a weird ... only spotted this driving home across the heath .... sideways!!!!!!! Tap the Compass pointer with your finger and it reverts to 'ahead' view.

No idea why ... but the rain sensor for the wipers seems to working much more sensibly than it had before ...puzzling, but I'm pleased about that.

Won't know much about mpg for a while as the ECU will start its learning sequence all over again over the next couple of hundred miles.

What is immediately noticeable is the reduction of smoke from the exhaust, and the smell of petrol vapour has completely vanished. Seems smoother and quieter but not hugely ... could be placebo effect. I should not have driven the works van in the morning ...that probably did it!!!

Whole task was around 3 hours ... Including a much needed cup of tea at the end!