Okay, been doing a lot of stervice stuff these days so I bought a diagnostic scan tool for 23 dollars and found out the code was an oxygen sensor.. But before jumping the gun and buying a 100 dollar plus replacement part. I also discovered a clip wasn't locked and so the air filter case wasn't fully shut which might have triggered an os code because of vacuum leak?. so I properly closed the air filter case and erasedthe code po135 using the scan tool thereby clearing the check light on my toyota. I have also been using injection cleaner in my last two full tanks of 87 octane reg. gasoline. So far, the engine check light hasn't come on again. My question is this, if it doesn't come on again, could it have been a vacuum leak as I suspected?. or could it have been the injection cleaner I used? If the scan tool diagnotic code specified a code for an os sensor, is it just the one sensor? Tia, jon

What kind of injection cleaner... if it's the stuff that costs under $10 a bottle it's a waste of money.

I assume this is an ODB2 car... the computers are really pretty good at targeting an issue. Better than amateurs are at second guessing them.

I'm guessing this car isn't fairly new... likely over 100K miles on it and its still the original O2 sensor... which does wear out or get contaminated and probibly overdue for replacement by now.

There are a lot of codes the computer can have... and I don't think you really fixed anything... you only temproarily cleared a code that's going to come back soon. A clip on an air fitler box, doesn't equal a vacuum leak. Unless your filter is seriously overdue for replacement... there should be minimal negative pressure at that point. AFTER the throttle body however... is a different thing.


If and when the O2 code comes back... replace it. You will likely find your fuel economy improves and it runs better afterwards.

P0135--Front HO2S Heater Circuit Fault (Sensor 1)

Ensure the pigtail is in great shape and not contaminated with oil, WD-40, silicone spray, or anything else. If all of that is fine, you will likely have to replace the upstream sensor (Denso only). Don't waste your money on other brands. Here's how to replace it yourself:

https://www.askmehelpdesk.com/cars-t...tml#post223376

You guys are terrific.. the check light finally came back on, yes.. my tundra has 127k.. the first os sensor was done by the dealer at 53k (bank 1 sensor 1) than bank 2 sensor 1 went at 83k and now again po135 or bank1 sensor 1 again.. toyota did the first two (expensive 339 first one and 350 second on think they get 200.00 labor fee.. I think I will learn to do this one myself.. I am pretty good with my craftsman tools and I'm not working full time so I have the time and can definitely use the savings. Is it recommended I clean fuel injectors if I haven't had them done professionally? Or is there a can of something I can pour in the tank? Jiffy said 80.00 for fuel injection cleaning. And should I have my catylic converter checked or replaced as well? My tundra runs nice and quiet and seems okay on gas. Tia, jon

What do I recommend... I got this advice from a Service manager at a Saturn dealer I was friendly with, he told me to do this rather than the far more expensive dealer cleaning service.

Run 1 can of BG44K from a full tank and do not top up until below 1/8 tank... do this every 30K miles and you are good to go.

Saturns had a problem with intake valves carboning up that interval... this prevented it from happening... and trust me go 34K without it and you have starting issues on that. And it still built up just like nothing was put in with the cheap stuff. But that cured it... I swear by it. Your smaller parts places that deal more with Mechanics will carry it, call around. I do that on all of my cars. Its in the ballpark of $30 a can, more or less. You only need one.

Don't worry about the cat converter until you have reason to do something... they aren't cheap.

With the O2 sensors, make sure the tips stay clean... and resist any urge to use ANY sort of lube or Anti-Seize on them... you WILL contaminate and ruin them. Install them dry and clean.

I haven't worked on a tundra, but be careful with the wires on the sensor. Break them and you end up buying a new sensor. Those are likely a four wire heated type.

Just FYI. The Tundra (4.7L V8 I presume?) Bank 1 is the drivers side, and bank 2 is the passenger side.
The smaller 3.4L V6 is the opposite. (4.0L too)
BG 44K bought from the dealer is money well spent. Every 30K miles, is just the ticket.
I put it in my Tundra when I fill up for a long trip and plan to use all that gas in one day.
One thing nice about the OEM sensors, is they come with a plastic cap over the threads to protect the small amount of anti-seize they put on them.
Just must be careful not to smear that upon installation.
Sometimes getting these back out after a while can be a real bear. In some cases, the whole manifold needing replace.

I will definitely get that BG44K asp.. also will take heed when replacing bank 1 sensor 1 os on driver side which is before catylic converter, not to use any lube to contaminate sensitive sensor.. ONE last question, and not sure if any could recommend this.. if using oem , which replacement brand is recommended? The at autoparts said it is about 108.00 with shipping and has the harness to make easy replacement.. plus he said it comes with easy step instructions to follow so I do not screw up an expensive part. I guess this is the way I'll go rather trying to be too cheap and risk splicing etc. thank you good people! You made my night! Lol

Denso.

Denso it is, I will first use that can of BG44K I just bought on eBay, after running it as recommended.. the whole tank in a day.. I will probably take a ice fishing trip way upstate ny for a round trip, that should do it. I will attempt replacing o2 sensor after that. Thank you again , jon

I take the can with me to the gas station... when at the pump... pour the can in the tank, then fill the tank up. And don't get fuel again until your gauge is down to 1/8 tank.