Oxygen sensor on exhaust error

[Kezzy1]

Hi,

The yellow engine warning light is illuminated on my mk1 yaris. The mechanic says the code is the 'oxygen sensor on the exhaust'. It passed the emissions test on the mot. He cleared the code but it has come back again. 

Any ideas what could cause that ? 

[doc_14]

Hi there.

 

Without knowing what is the error code, is difficult to say what the problem is.

It could be as simple as a Heater circuit fault, a lazy sensor, even can be the sensor givving bad readings and can have emissions a bit above the normal but within the limit for passing the MOT test. Do you feel any difference in the car?

[Kezzy1]

Po135 oxygen sensor heater circuit bank sensor 1

My yaris mk1 was unused for 'a long time' before i bought it. I guess that means 1year+ ? 

It resets and stays off for a couple of days then pops on again. 

Yes, it passed the MOT last month. 

The dashboard screen is showing i'm getting 36mpg. Is that about right ?

 

[wildtapholer]

I was told just taking the warning light off and not repairing the problem will eventually result in the cat failing, a new oxy sensor is a lot cheaper than a new cat. My brother in laws new car(well new to him, 2004 meriva) was doing the same, I kept removing the warning light for him every week  after he bought the car and we found the previous owner had done the same for a month before they sold it, warning light has never been back on since replacing it.

[Kezzy1]

5 minutes ago, wildtapholer said:

I was told just taking the warning light off and not repairing the problem will eventually result in the cat failing, a new oxy sensor is a lot cheaper than a new cat. My brother in laws new car(well new to him, 2004 meriva) was doing the same, I kept removing the warning light for him every week  after he bought the car and we found the previous owner had done the same for a month before they sold it, warning light has never been back on since replacing it.

New sensor ordered up !

[wildtapholer]

I assume your mechanic is doing it, it's straight forward if you have the proper tools, but can be a pig to remove, a bit of heat helps, I didn't have the proper tools and took me over an hour, had to drop the exhaust to get a proper grip on the sensor.

[Kezzy1]

Swapped out the sensor for new. I can rely notice difference on engine. Immediately seeing 40% improvement on mpg around town.   Looking forward to taking it on a long run and seeing what the mpg is on that.

[Cyker]

Awesome! Glad you got it fixed, and thanks for posting back to let us know how you got on!