three faulty O2 sensors!?

[Optimus prime]

Hi Guys,

The car threw a CEL at me a few weeks ago with P0155 (bank 2 sensor 1) which is the left hand sensor on the mani.

I reset the ECU by disconnecting the battery and swapped the two sensors over and the problem followed the sensor as I got a P0135 which is the same O2 heater circuit fault but now on the right hand side (as expected).

surely enough I think that proves the sensor is faulty so i purchased a sensor from a good, well know breaker.

I swapped the sensors back so the car threw a P0155 just to confirm my findings. i then replaced the left hand sensor with the new, used sensor and reset the ECU again. i took it for a test drive and when the car hit nominal temperature it gave me another P0155.

Thinking this sensor is faulty i told the breaker and he got another out to me. i fitted it this morning and i got the same P0155 CEL.

What am i doing wrong! is there something i'm missing or have I just got really unlucky with the replacements?

any advise or experience would be gladly welcomed to help me out.

Cheers

[McMr2]

I believe they can be a bit delicate, is it possible they are unhappy with being swapped about or damaged in transit? Seems unlikely to have 3 in a row mind.

Alternative is something causing them to fail in situ, but I don't know what could be doing that in such a short space of time.

[paulj]

I think the sensor only connects to the ECU once operating temperature is reached and sustained 2000rpm is seen, you might have not got a CEL code if you didn't trigger these conditions.

Also check if your sensors have previously been replaced with generic ones which needed the wiring spliced, it could be a break in the wiring perhaps on a corroded joint rather than the actual sensor failing,

The sensors are really fragile and don't always behave.  If you search car parts sites you can get new ones at around £50 each - perhaps even cheaper with black Friday looming.

[Optimus prime]

thanks for the input but surely swapping the sensors and seeing the problem move to the other bank eradicates any other 'upstream' faults?
I will swap them over again tomorrow and see if the problems swaps sides again. in fact, i will swap out the potential good one to see if i get 2 CEL's.

If it looks like i have another faulty one i might just purchase a new one like you say.

[Call the midlife!]

How long are you disconnecting the battery for? It might just be you've not fully discharged the system the last couple of times?
If you press the horn with it disconnected it will help drain whats left, that's if you're not using the code reader to clear the codes?


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[Optimus prime]

in both case's the battery had been disconnected for hours beforehand. on the second replacement I even reset the code via the OBD2 interface

[Call the midlife!]

in both case's the battery had been disconnected for hours beforehand. on the second replacement I even reset the code via the OBD2 interface

Yeah, you'd think that would be enough [emoji38].
Wonder if it's a bad connection in that particular plug?


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[paulj]

Good thought midlife, perhaps one of the male contacts pushed back into the plug assembly and not making contact......  not sure which side is male on the wiring but if its the loom side it could be just that.

[Call the midlife!]

Good thought midlife, perhaps one of the male contacts pushed back into the plug assembly and not making contact......  not sure which side is male on the wiring but if its the loom side it could be just that.

If it's the heater circuit it narrows it down at least, you know which wires supply it.


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[Carolyn]

As has been said, they are very delicate, especially the heaters and especially when they have some age on them.

Just the act of taking them out, posting them and putting them back in can be enough to do the damage.

So the original failed and then two used replacements?  If so, that's unlucky but not unlikely.

If the problem is following the sensors when you swap, that rules out connections, doesn't it?  Just leaves the sensor?

I gave up on used ones some time ago.  A new one seems expensive, but you can get genuine Denso with no plug and do some soldering if you want to save a bit.

[Ardent]

New is the way.
When you figure in your time and messing about, probably cost more than a new one already.

[BahnStormer]

I ended up getting all 3 of mine replaced with new (Opie oils was cheapest)....

This might be helpful as it removes that seemingly random element of when the errors resurface.

The "confirmation driving pattern" is
- turn engine off
- ignition on and idle for 2 mins
- drive at 24+ mph for 20sec or more
- idle for 20sec or more
- drive for 20sec at 24mph+
- idle for 30sec

I can't recall if that only applied to the post-cat sensor or all of them.... but it will allow you to give the car the right type of run aroudn the block to re-trigger the error

[Optimus prime]

I'm now on my 4th secondhand lambda and that also has failed on the heater circuit. I can vouch for the Lambda's being at fault as I have 1 good sensor that I can swap with any of the faulty ones in situ and the fault code for that bank disappears.

I've seen the 'resistor' mod to the heater wire on the sensor. Doing this won't cause any problems will it?

[Carolyn]

If you don't mind doing a bit of soldering.  Here's a Denso that will do the job:

https://www.ebay.co.uk/itm/DENSO-Universal-Fit-Lambda-Sensor-DOX-0109-Oxygen-O2-Genuine-OE-Part/172991630388?fits=Car+Make%3AToyota&epid=1482187951&hash=item28471acc34:g:2z8AAOSw3KFWgrV4:rk:14:pf:0

[thetyrant]

Not worth messing about with used sensors in my opinion just get a new one, either universal or direct fit, if you do go universal you have to crimp the wires to join them to factory plug as wires are not suitable for soldering on lambda sensor due wire strand type, ive just replaced one of mine with a new one i bought for my old rav4 before it died and plug needed changing to suit MR2, no problem i thought just swap and solder and had a hell of a battle despite soldering professionally for years, some searching found the reason is the wire type used on these.

Also some say wire needs to breathe which soldering messes up but not sure how true all that is tbh.

[Carolyn]

Not worth messing about with used sensors in my opinion just get a new one, either universal or direct fit, if you do go universal you have to crimp the wires to join them to factory plug as wires are not suitable for soldering on lambda sensor due wire strand type, ive just replaced one of mine with a new one i bought for my old rav4 before it died and plug needed changing to suit MR2, no problem i thought just swap and solder and had a hell of a battle despite soldering professionally for years, some searching found the reason is the wire type used on these.

Also some say wire needs to breathe which soldering messes up but not sure how true all that is tbh.

That's handy information.  All the more reason, then to just get a new Denso with a plug on it?  Crimping done by a beginner is pretty unreliable in my experience.

[1979scotte]

This thread is evidence enough for menthat secondhand sensors just aren't worth the bother.

[Optimus prime]

OK i'm not going to bother with anymore used ones. the heater element is way too delicate to be sent by post on a used unit.

I'm thinking about giving the resistor trick (RS 160-736) a go, as done by Lee, here:
https://www.youtube.com/watch?v=H6mX4efePx8

Failing that, I think it's time to buy this (I think that's the right one):
https://www.sparkplugs.co.uk/denso-oxygen-sensor-dox-0204

[thetyrant]

OK i'm not going to bother with anymore used ones. the heater element is way too delicate to be sent by post on a used unit.

I'm thinking about giving the resistor trick (RS 160-736) a go, as done by Lee, here:

Failing that, I think it's time to buy this (I think that's the right one):
https://www.sparkplugs.co.uk/denso-oxygen-sensor-dox-0204

I wouldnt bother with resistor just buy the new sensor you linked its cheap enough, remember these sensors ensure the cars fueling is correct so critical to a healthy engine and good mpg, not having working heater circuit isnt end of the world as they are mounted so close to engine on these cars they will soon warm up, but to me for that price i would just but new and do the job right

[Optimus prime]

I do agree but the price difference of £2,00 to £50,00 is quite a step up to solve a problem that doesn't affect engine performance.

I hate decisions like this, I suppose my brother will only get one Christmas present this year.   

[SteveJ]

.

[thetyrant]

I do agree but the price difference of £2,00 to £50,00 is quite a step up to solve a problem that doesn't affect engine performance.

I hate decisions like this, I suppose my brother will only get one Christmas present this year.   

Just put some tape over EML light then even cheaper