schan1w

I keep getting a check engine light and an O2 sensor trouble code. I've been avoiding replacing it because the car has 205K miles. I have a code reader and just erase it when it bothers me and the last time I had a smog check, I just erased it right before the inspection. Is there any long term damage from not replace one faulty O2 sensor? It is bank1 sensor 1. Thanks for any info.

masagsxr

You might have a leak somewhere between the exhaust manifold and the cat which is why it is not getting good reading and throws in a CEL.

I'm surprise they you passed smog. Usually after resetting it, you can't just smog it right away. ECU needs to collect some data that the smog machine needs to read and you'll need to put about 10-15miles of driving before getting it smogged. If you do have about that much miles after resetting, then you probably do have a leak or the o2 sensor(s) themselves are starting to go bad.

schan1w

The CEL is thrown after about 10-15 miles after resetting it. How can I tell if it is a leak or a faulty O2 sensor? I think the trouble code was P0135.

Lexmex

masagsxr hit it on the head

There's something known as readiness monitors and those won't be set immediately after clearing the code, 10-15 miles driving usually does it (I like to do a 50/50 highway/city mix with at least getting over 55 mph on the highway, but even then it can take a bit longer). Most OBD2 scanners these days can show the readiness monitors and then see if everything is set.

That particular code is an upstream A/F (air fuel sensor), but I'd have to know what your vehicle is exactly to help you a bit more.

I just recently replaced the A/F sensors (there are 2 of them in my RX300) and not yet replaced the O2 sensor after the main cat below (that's a different code). For a while, and in large part given to my driving in Mexico for over 6 years (think gasoline quality) those a/f sensors had a rough life. For a while, those sensors have been giving my codes on and off, but I finally decided to clear them out once and for all, and have not received a single a/f sensor code in several weeks.

Those old a/f sensors I had, while not dead, were certainly deteriorated and I would via laptop diagnostic equipment note they were often out of range when checking the parameters on both banks.

If there is going to be a leak per se, you are going to have to take a look at the areas from the exhaust manifold down to the a/f sensor itself (let me know what vehicle we are talking about and I can help a bit more). I usually run my hand very carefully after starting up the vehicle and see if there is hot air. I had to have a piece of my manifold welded to due to a leak in Mexico, so it's not uncommon.

If no leak, and if you do not have access to software or an OBD2 tool that can show the readings on the bank, some mechanics have such tools and often can show a freezeframe reading at the time an error occurred.

The longer term effect of a deteriorated or even busted a/f sensor is increased fuel use, because it goes into a default setting for the air/fuel ratio.

At your mileage, it's bound to happen and I generally would replace both unless you are thinking about selling it in the near future.

Amazon.com has probably the best prices I have seen on a/f sensors and that is where I got mine.

Again, let us know the vehicle we are talking about.

schan1w

Hi Lexmex, it's a 95 ES300. Thanks for any info.

Lexmex

The particular sensor for that particular code is a Denso 234-4623 (rear) that corresponds to a bank 1, sensor 1 code, P0135

If you had a code like P0155, that would be bank 2, sensor 1, Denso 234-4622 (front).

These are some other thread on that subject of the P0135, https://www.clublexus.com/forums/es3...io-sensor.html

https://www.clublexus.com/forums/es3...cel-p0135.html

If it were P0155,

https://www.clublexus.com/forums/es3...o2-sensor.html

Amazon had some good prices just type in the sensor number 234-4623 and see what you come up with.

masagsxr

Yup... I'm using scantool . net and whatever software I got from them that was free. It does have freeze frame readings.

schan1w: Go under the vehicle and just have a look it is really easy to tell if you have a leak or not. Again, depends on the mileage and how you take care of the car as far as type of gas etc. It could be of old age. It is a 15year old car afterall and you probably do need to replace the sensor(s) already.

masagsxr

I've always thought Bank 1 is Sensor 1 (front) and Bank 2 = Sensor 2 (rear).... now i'm confuse...

toy4life86

iTrader: (4)

Since your OBD1 and not OBD2 thats how you pass the inspection I have driven with bad o2 sensors before but i think you should correct it it will probably save you gas too but cant it also be a cat?

schan1w

Thanks. I decided not to be a cheap *** and just ordered the part. I've been delaying a lot of things .... fixed window regulator and antenna mast last week. Had a shop replace the transmission gasket before that - I didn't want to deal with the mess and get under the car. Next will be O2 sensor and AC expansion valve. But she's served me well and is running great, so I guess I cannot complain. My wife drove this car for 10 years and the last 5 has been mine. I hope to get another 5 years out this car (knock on wood)... Timing belt has been overdue since 180K miles.

oguitar

A bad o2 sensor is not good for your car. It controls a lot of the fueling and could cause you to run rich or lean depending on how the sensor fails.