Oxygen Sensor Bank 1

[Dale H]

After having an engine warning light come on it has been diagnosed as a faulty oxygen sensor in bank 1 as the culprit.

I have read Les's very useful guide and am confident that I can replace the sensor myself.

Only problem is I don't which one is bank 1. Is it the one to the left or the right of the manifold

[cfc1]

Would need more info...

Bank 1 sensor 1 or bank 1 sensor 2?

What was the code... I would guess p0141?

[Dale H]

Would need more info...

Bank 1 sensor 1 or bank 1 sensor 2?

What was the code... I would guess p0141?

Ahh not sure. I didn't read the error code myself so I'll give the garage a call tomorrow to see which one it was.

Any ideas which side is sensor 1 and sensor 2?

[curriedb]

It's a VERY common problem with the MK3s. Once you have the code you can easily identify which of the three sensors it is!

Looking into the engine bay you will see two sensors:

The left one is Bank 2 sensor 1

The right one Bank 1 sensor 1

If you look UNDER the rear left hand bumper you will see a third sensor: Bank 1 sensor 2 (likely culprit as Davy says)

...also have a read of this:

www.autotap.com/Articles/Understanding_Oxygen_Sensors.html

I BELIEVE the torque setting for the sensors is 33 ft lbs - but you need to get this confirmed...

Good luck

Dave

[Dale H]

Ok thanks guys, will check code again and get back...

[Dale H]

Would need more info...

Bank 1 sensor 1 or bank 1 sensor 2?

What was the code... I would guess p0141?

Right - I've got the error code and as you thought it was P0141. I now know that is bank 1 sensor 2 - the one under the bumper.

Firstly is it essential to remove the rear bumper to replace the sensor?

And also, before I order it, is this the correct part: http://www.cats2go.co.uk/Default.aspx?PageID=15&CartID=1

Any help is much appreciated

[cfc1]

P0141 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

This is the Post Cat (the one after the cat) sensor

Your link isn't pointing to any particular sensor or showing a price... so....

Look here... http://oxygensensors.com/catalog.php?&pkey=1432925

Put in your car details..

It will give you a choice of a few brands (all descent makes) and whether you want OE or Universal... Universal ones will require you to cut off the plug from your own sensor and splice it onto the new one, OE comes complete with the plug so it's just a case of swapping them out.

[GIDDLEPIN]

Would need more info...

Bank 1 sensor 1 or bank 1 sensor 2?

What was the code... I would guess p0141?

Right - I've got the error code and as you thought it was P0141. I now know that is bank 1 sensor 2 - the one under the bumper.

Firstly is it essential to remove the rear bumper to replace the sensor?

And also, before I order it, is this the correct part: http://www.cats2go.co.uk/Default.aspx?PageID=15&CartID=1

Any help is much appreciated

Hi Dale

As long as you have the correct socket this job is really easy ;)

Here's a vid taken of me changing all three sensors in under 5 minutes CLICKY

[Dale H]

Superb! thanks guys. Will let you know how i get on. :)

[curriedb]

Dale H

22mm slotted socket readily available. A quick search suggested this is quite a good price to pay (as many companies are charging circa £5 postage for single items) http://cgi.ebay.co.uk/DRAPER-22MM-3-8-LAMB...id=p3286.c0.m14 This is just an example - I'm not endorsing the supplier!!

Davy has - rightly - pointed you in the direction of America - if you want to buy a sensor at a reasonable price. UK prices are normally MUCH higher. Here's an example (for price comparison purposes only): http://www.gendan.co.uk/oxygen_lambda_sens...Toyota_MR2.html

Here's an alternative American site - to the popular one Davy mentioned - that sells O2 sensors: http://www.rockauto.com/catalog/x,carcode,...3,parttype,5132

Dave

[curriedb]

Given that the P0141 code seems to be the most common trigger of the MK3's MIL ..I notice that some clever people over on the Mr2ROC site have taken to isolating the heater wires from the post cat 02 sensor and splicing a 15 ohm (circa 35 watt) resistor in place instead. I assume this fools the ECU into thinking all's well - so no light comes on!

Any thoughts on this VERY cost effective method of solving a common problem? It's certainly cheaper than buying a new sensor - if it's only the heater-circuit of the sensor that's failed.

Dave :)

[cfc1]

The resistor trick fools the ECU into thinking that the sensor is at full operating temperature. A few members on MR2roc have done this with no problems as far as I'm aware.

[curriedb]

The resistor trick fools the ECU into thinking that the sensor is at full operating temperature. A few members on MR2roc have done this with no problems as far as I'm aware.

Thanks Davy...thought it was worth 'airing' - given how often this topic crops up!!

If you are reading this topic after hitting the 'search button' in panic mode. Here's a quote (courtesy of ROC) on the subject which should help you relax a little...

Quote:

"The P0141 code is an advisory code, it has no effect on the actual running of the engine...

The code refers to what we call the 3rd O2 sensor, but is more accurately called bank 1, sensor 2. There are 2 other O2 sensors on the engine, known as Bank 1, Sensor 1, & Bank2, Sensor 1. These 2 are responsible for measuring the fuel air mix that has just been burnt and exhausted by the engine. There are 2 of them because Toyota's ECU actually runs this engine as 2 separate entities, i.e. it treats it as 2 two cylinder engines. Weird, but effective.

The 3rd O2 sensor is fitted downstream of all the cats, whereas the 2 metering O2 sensors are fitted upstream so that they can measure the raw, un-catalysed gas coming out of the engine. Its only job in life is to measure the O2 content of the exhaust gas after the cats. The ECU then compares this reading to the one it took from the Bank 1 sensor in the manifold. The logic it then applies to the 2 readings is astonishingly simple:

If the 2 readings are different, and more importantly the reading from the 3rd O2 sensor is more stable than that on the manifold O2 sensor, then all is well with the world. It means that the ECU knows your cats are working as they have changed the make up of the gas.

If the 2 readings are the same, then the ECU knows that the cats are doing nothing to the gas at all, and lights the CEL, which prompts you do go and have your wallet lightened by your local dealer...

Because there's no effect on the closed loop control of the Fuelling, the engine management makes no changes that would effect power, or economy.

You don't actually have a failed O2 sensor though, I'd bet good money that if I hooked up my OBDII reader to your car, I'd see sensible readings coming from the 3rd O2. what you actually have, is a failed heater element.

Each O2 sensor has a built in heater inside it. The heaters are used to get the Zirconia measuring sensors inside them up to operating temperature quickly so that they can get on with the job of measuring oxygen. This gains vital seconds in the process of gaining efficient emissions control on a cold start of the engine. Once the engine is hot, clearly anything in the exhaust flow isn't going to be in need of heaters! The ECU monitors these heaters by measuring the current going to them, to much or too little flags up the fault code you have at the moment. The sensor itself is still working, it just takes a while to warm up... Again, having a duff heater in an otherwise functional 3rd O2 sensor wont cause any problems with engine management.

So, what to do to fix it? Well, you can replace the unit, or you can ignore it... Either way your car will go just as fast as its always done, using exactly the same amount of fuel. The problem with just leaving it, is that with the engine light already lit, you wont see any new problems should they occur. Fixing the thing is expensive, especially considering all you are going to gain is clear dashboard.

I applied a bit of electrical tom-foolery to mine when it went, I simply connected a high power resistor to the heater circuit on the sensor, so that it drew the "correct" amount of current from the ECU, That way ,as far as the ECU was concerned, the heater was working, and after 2 full start -warm up - drive -stop- cool down cycles of the engine, the light goes out. Simple..."

[Dale H]

Thanks for all the help and advice guys. Changed sensor at the weekend and so far (touch wood) light has stayed off.

Cost just under £60 for the new sensor and socket and was easy to replace even by a complete novice like me :-)

[cfc1]

Well done... glad you have it sorted.

[curriedb]

Yes, it's good to know you've replaced the sensor, Dale H, and got rid of the dreaded MIL light! Well done...you have passed the initiation ceremony for the MK3 section with flying colours :)

[Woolymammoth]

Hi Guys,

I thought i would share this with you as a lot of these threads are all over the place and not clear on what to do, this is the cheapest fix i have come up with for your engine management light being on solid not flashing and the dreaded o2 sensor replacement.

1 : Firstly try cleaning your MAF sensor with a tin of carb spray see the link under technical information hints and tips....MAF sensor cleaning will cost you nothing..

http://toyotaownersclub.com/forums/index.php?showtopic=63346

2: If that does not work check all your fuses to see if any have blown.

3: If that does not work you need the error code to find out which of the 3 oxygen sensors have possibly gone, there are 2x pre cat, 1x post cat.

Now there are 4 ways of doing this, Mr T or a garage can do a diagnostics which will cost you about £40, or if you know somebody with a handheld diagnostics machine that can do it, or there are some guys on this site that offer to read your error code for free they have a hand held diagnostic machine you can use just follow this link:

http://toyotaownersclub.com/forums/index.php?showtopic=85601

or you buy one off eBay an OBD2 reader for about £25 , the 16 pin diagnostics connection is under the drivers side dashboard at knee height, or the way i done it:

If you are covered by a breakdown service, i am with the RAC, phone them and say your engine management light has come on i have pulled over to the side of the road and need assistance, i need your guy to come out and tell me if it is safe to drive my car to a garage, insist on them coming out.

They did come out for me and he pluged his diagnostic machine in and give me the error code for free.

The error codes i have found on these forums are :

Po141 or 0120 O2 sensor heater circuit malfunction bank 1 sensor 2 ( post cat sensor under the bumper )

Po135 O2 sensor heater circuit malfunction bank 1 sensor 1 (right hand side of manifold pre cat sensor)

bank 2 sensor 1 (left hand side of manifold pre cat sensor)

4: So now you can either go to Mr T or a garage which will charge you about £250 to replace one sensor or you can purchase the O2 sensors in the UK, i have just got a price they are roughly £80 each and they are the cheapest you can get or:

Get them in America copy and paste this link in your browser

http://www.automedicsupply.com/index.php?&...&height=768

You can get your oxygen sensors and the socket you need to get them out and delivery for half the price of any where in the UK seriously!!! so all 3 sensors plus the socket costs you about £120.

5: Then you can fit them yourself with the pictorial guide Les has made in technical information hints and tips oxygen sensor replacement :

http://toyotaownersclub.com/forums/index.php?showtopic=83024

6: Lastly after you have fitted your sensors you need to reset your engine management light on the dashboard, instead of taking it to Mr T who will charge you £50 for the privilage, simply disconnect your Battery for 10 minutes and it will re set your ECU

and if you have cured the problem the engine management light will stay out.

I hope this will help a few people, as this site has helped me save a fortune, Les you are a Mr2 God!

Neal

[Dans555]

Hi All,

I've just joined and found some excellent stuff on here already about my P0141 fault code!

I'd like to give fixing the Bank 1 sensor 2 fault myself.

I have an SMT version, with standard factory fitted twin exhaust, can anyone point me in the direction the most current best quality/value for money direct fit replacement? and the same for the tool require to fix it. I've searched around & i'm getting myself confused!

Cheers

Dan

[cfc1]

o2 sensor socket for removing the old one and fitting the new one.. you need 22mm...

http://shop.ebay.co....osacat=0&bkBtn=

Replacement OEM sensor...

http://oxygensensors...p?&pkey=1432925

Put in your cars details and look for the Post-Cat OE Sensor for a direct replacement.

[Dans555]

Thanks for that i've ordered the socket, I went to order the o2 sensor from that site but it won't let me change the shipping address to the UK? have you had any issues with this?

[Dans555]

Thanks for that i've ordered the socket, I went to order the o2 sensor from that site but it won't let me change the shipping address to the UK? have you had any issues with this?

I've emailed them now, hope they can ship it to me!

[cfc1]

They should be able to ship it to you OK, I've never had the need to use them but I know people who have, without any problems.