james250

I replaced the 2 Air/Fuel ratio sensors in the engine bay. Fuel economy has improved since. Haven't touched the sensors post-cat though.

I reset the code last night one the way home and drove home which was about a 15min drive. Will clean fuel cap area while the cap is closed and then inspect it so dirt doesn't fall in and go for a drive tonight. After that if light hasn't come on I'll plug in the reader and see if it's sitting as pending

How long does a pending code stay before it becomes a stored code? If I were to get a pending code show up before the MOT and then I clear it before the car is tested, it will then have to go to pending and stored but while they test the car they leave it on for the duration of the test which is about 45mins and rev it too, so wondering if the light can come back on while they are testing it? Also, if it was the fuel filler cap, will the error not be more related to something about EVAP? Or is this code also related to EVAP? My fuel cap area is rather dirty, I'll give it a good clean and check the cap. Anything in particular to look for on the cap?

The warning light I cleared it last night. What's the easiest way to see if there is a leak somewhere in the exhaust other than loud noise? I don't the exhaust being loud.

It's strange because this happened about 8miles into driving after I filled petrol. I didn't fill the tank though. And I'm sure I tightened the filler cap.

You mean a hole in the exhaust where the a/f ratio oxygen sensor is? I'm guessing it can also be a pin hole anywhere in the exhaust right? The car has done over 130k on its original exhaust. The pre-cat oxygen sensors are new but the post-cat are still original ones. How do you locate an exhaust leak?

While driving on the motorway today my check engine light came on. Scanned the code and it reads: P0420 - Catalyst System Efficiency Below Threshold Bank 1. I have new Air/Fuel Oxygen sensors and have had them in the car for nearly a year now. What is this code and any ideas how to fix? For now i've cleared it to see if it returns but as with past experiences with codes, they do always seem to come back until the root cause is addressed. I have an MOT coming up this week so not the best time for such code to pop-up. Any advice?

I've turned the child lock latch on both of my rear doors and on one of the door it works and I cannot open it from inside but the other door even though the latch is down it doesnt actually work. Any ideas what is wrong?

I need to replace my windscreen through the insurance. I was hoping to do it when weather gets better next year. But coming up to MOT time and the crack is very long but its on the passenger side. But I read on RAC website, if the crack is larger than 40mm anywhere on the glass then it is a fail. So my question is, does the adhesive they use for windscreen set and cure properly in this freezing weather?

So technically you could just pop the levelling rocker switch out, hide it behind the panel and put a blank rocker switch cover? and then they wouldn't know it's not factory fitted 🙂 Out of curiosity, the rule is that existing halogen headlamp units cannot be converted to be used with HID bulbs right? From what I have read and I spoke to few MOT testers who said you can replace the entire headlamp units with OEM HID units and that's fine. But when you do that, you will still have the rocker adjustment switch like you do, so I don't think an MOT tester can go based on that adjustment switch like your tester has done.

Just a quick update. It's been a while but I did get this problem solved. It was the dodgy fake denso sensors from america. I ended up getting the DOX-0263. This is the item that the Denso Europe part finder was telling me I needed and had the same OE part number. I installed this back in March and so far it's been good.

Thanks for the offer, much appreciated if only you offered earlier LOL. I ordered a pair of new Genuine Denso ones from UK denso supplier. Will see how that goes and keep you guys posted.

Sorry for late reply about this. got really busy at work so car work had to be paused. Anyway, finally got round to running Techstream on the car and below is a screenshot of what I got. Whatever RPM i was doing it wasn't really moving much in terms of voltage. I assume these AFS sensors are no good. any thoughts?

I also read that under the new rules, vehicles that emit ‘visible smoke of any colour’ during Mots will be assessed as a major fault and issued with an automatic fail. Doesn't the is250 pretty much always have smoke in cold weathers?

Just installed techstream. Going to play around with it later. What section is the error codes stored and pending in? Is there different sections for error codes?

Agreed. All the points are good. Too many dodgy hid installations. If someone really wants hid they should get the correct headlight housing for it. Brake fluid testing I think is way over due and is a very good thing.

Sorry might sound silly but i'm a bit lost. Do you mean disable reporting too much data to reduce data reading lag? So the more data it is reading the more lag there will be? is that what you mean? How do you select the data that you want only? and what is the ms reading you are referring to?

@johnatg thanks. Those are great screenshots. Will see how mine looks when I connect it up. Will post an update once I have done so.

An interesting video, seems to show Techstream being able to read AFR data. Surely if the Intelligent Sensor can read data via the ODB port then why couldnt TechStream. As long as the software is capable of it.

I got pm'ed the link from another lexus forum but was told it's from the lexus service manual. I think it says start engine and run it at 2500rpm for 90 seconds to Warm up the Air-Fuel Ratio sensors. After that to do the 3 scenario monitoring. But i guess will there be any harm waiting longer to warm the engine as my engine hasn't been started this week so it will be really cold so would think might be worth while running engine for a bit before hand

My techstream finally arrived. Somehow went missing in the post so had to be sent out another one. Going to install it this weekend and try it out. I just came across the following tech diagram that also refers to diagnosing the AF ratio sensors. But it for some reason has different instructions to the one @Shahpor posted. So it's a bit confusing. Based on the diagram below, am I correct in understanding that the procedure is asking to start the engine and run the rpm at 2500 for 90 seconds then go to the relevant section in techstream and carry out the 3 scenario tests that it lists. Based on the standard voltage table, the reference column says that scenarios 1 and 2 which is running idle and running at 2500rpm should both be between 3.1v and 3.5V. So that's a fluctuation of 0.2V each way. and scenario 3 should apparently see the voltage increase to 3.8V or more and then drop back. Is this understanding correct? Also, the second diagram i have attached is of a table that shows Lean and Rich voltage. It shows if voltage is 3.0V then it's rich and if 3.35 or more then it's lean. But that doesnt seem to match the first diagram. Or is the second diagram referring to if the ECM injects +25% fuel then in that condition the voltage of 3.0v or less will be Rich. And if ECM injects -12.5% and a voltage reading is 3.35 or more then it's a Lean situation? I guess we don't have a way to know how much fuel the ECM is injecting to do this comparison do we with techstream?

It's definitely not downstream sensors. they are AFR sensors for sure but I now believe they are fakes. Because on the side of the box it had a photocopied colour toyota barcode. I am still waiting for my Techstream to be delivered to run live data on the sensors to see what kind of readings they are giving. If they are off I think I will go for the DOX-0263 as I believe those are the correct Denso equivalent in Europe.

From all the research I have done, it seems that the European Denso sensors have different part numbers. I have no idea if the hardware itself is different. I checked with a few Denso suppliers and they all confirmed that DOX-0263 fits the Lexus IS250 upto 2008.

Also further to my post above, I found the following youtube video which shows someone installing the DOX-0263 on IS250. It's not in English but the at 1minute in you can see the packaging that says DOX-0263

@is200 Newbie and @normski2 I may be changing the sensors I got if it turns out they are bad. However, I am slightly confused regarding the part numbers. Upto 2008 Is250 has a OEM part number of 89467-30010. Now if you go to the densoautoparts website or rockauto website they give a denso equivalent part number 234-9051 which is what you purchased @is200 Newbie and for 2008 onwards they give denso part number 234-9048 and 234-9068. So if you actually go to most popular sites and auction sites you will actually find that no-one in Europe sells Denso part 234-9051. Even Denso Europe do not have this in their catalogue. It appears that to the European market, Denso Europe part numbers are completely different and here is my findings. Note: the reference website is Denso Europe website which is: http://www.denso-am.co.uk/e-catalogue/ these are the people who companies like Euro Car Parts etc deal with to stock Denso parts. According to Denso Europe website, the Denso Equivalent part number for 2005-2008 is DOX-0263. If you go into the specs of this as in screenshot below it matches the same spec as the one from the American Denso part number. The part number for 2008+ is DOX-0506 and according to the specs the main difference is the length of the cable. If you look up the tech specs for the DOX-0263 it appears to fit the IS250 upto 2008. I went to Euro Cart Parts website and they have the Denso sensor advertised at over £329.99 each which is ridiculous. But it states it fits the OE number. So I spoke to Euro Cart Parts to see what the Denso Part number they have for that product is and they confirm that the Denso Part number is DOX-0263. The DOX-0263 is much more reasonably priced than the OEM toyota ones and you can get them only varying between £90 and £100 each. Not sure if anyone else has any experience with this. But there is not much info out there. And it appears the DOX range is a european product code with a EAN number.