EML been on for six years with no apparent problem but MOT due.

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mainbunny

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You're replying to yourself now.
It's the after/post cat sensor a four wire and has a heater element that's why the code is, P0141 O2 Sensor Heater Circuit (Bank 1 Sensor 2). This can be caused by a simple failure or as a result of oil wicking into the wiring harness on the M271 engine. Changing it without fixing the oil problem will result in another failure and lots of other odd problems.
Thanks buddy..
 

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Torque only gives you the short code (4 digit) rather than the full code which can give a much more precise diagnosis.

Have seen several times where the full code says the reading is out of tolerance with another sensor and it is actually the other sensor which is the issue.

I would find a local Indy who can put it on Star and get the full diagnosis of the issue.
 
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mainbunny

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Torque only gives you the short code (4 digit) rather than the full code which can give a much more precise diagnosis.

Have seen several times where the full code says the reading is out of tolerance with another sensor and it is actually the other sensor which is the issue.

I would find a local Indy who can put it on Star and get the full diagnosis of the issue.
Thank you Stu, that's exactly what I've just decided to do..Appreciated..
 
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Thank you Stu, that's exactly what I've just decided to do..Appreciated..
Purely hypothetically what would stop me from connecting the eml
Then, as you say the eml has no effect on the car's performance, why not get a code reader to douse the light just before the Mot.
It will come back on later, but you will have passed the Mot and it will have cost you next to nothing.

I disconnect the egr valve on one of my cars by simply unplugging it. The eml shows up, but I reconnect the valve just before each Mot, and douse the light with a scanner. Not a problem.

No point just swapping parts in the hope that you will eventually hit the right one. That's the road to automobile bankruptcy.

Purely hypothetically what would stop me from connecting the eml in parallel with say the ignition smd led,(typical ex tv engineer thoughts) :)
 

umblecumbuz

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If you're going to all that trouble, just disconnect it.
Of course, if another more serious fault ever shows up, you've lost your early warning.
 
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mainbunny

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If you're going to all that trouble, just disconnect it.
Of course, if another more serious fault ever shows up, you've lost your early warning.
They check the light comes on during the MOT now so not viable anymore sadly..
 
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mainbunny

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P0141 O2 Sensor Heater Circuit (Bank 1 Sensor 2)
Looks very much like your heater circuit is faulty.
The after cat sensor has a heater circuit to help it on start up to read the correct levels.
This can "burn out", it is easy to test with a multi meter. There should be two of the four wires the same colour measure ohms across them it should be low (from memory 10 or so) don't touch the others on resistance setting.
Edit. I'd go with a Bosch, I got one on ebay for £40.
Oh, have a good look in the connector for any sign of oil as the oil actually "wicks" through the copper strands of the wire from the cam magnets which may need changing or at least blockers fitted as it is not a leak as such.

Just as a matter of interest was thinking about the heater circuit of the sensor so I turned the key to the click before turnover, waited five seconds to maybe give the heater a chance to warm up and amazingly it didn't trigger the code, pretty sure you're right Oldspanners...
 

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Just as a matter of interest was thinking about the heater circuit of the sensor so I turned the key to the click before turnover, waited five seconds to maybe give the heater a chance to warm up and amazingly it didn't trigger the code, pretty sure you're right Oldspanners...
Usually the heater in the O2 sensor works immediately or not at all ie is broken but there may be another reason.
There is an inlet to the sensor to allow it to compare the O2 levels it may be partially blocked.
Really just guessing without codes or visually inspecting.
 
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This may be of interest to you guys and continuing from my lit EML (which now appears to work normally ;) )....I installed the app 'Torque pro' on my phone, (found a freebie), it's paired with the dongle plugged into the ECU connector £5 ish, also paired with the car audio system...Starting the car from cold the app is set to 'speak', it very shortly says '02 Sensor heater problem, PO141, fault cleared', ( another option is to clear the fault after warning you of it )...So basically turns off the EML after fault register, I'm sure you know where I'm going with this, (could have saved me a hardwire mod but never mind), two different fault codes were 'spoken' a few minutes later followed by 'fault cleared'...Another few minutes it says 'Engine reached operating temperature', from then on no more codes were triggered at all even after a long drive.. Could have spent a fortune as was mentioned, but it appears it's just the warm up that caused the problems... Hope this may help someone who has similar problems and maybe coming to an MOT....
 
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mainbunny

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Just to let you guys know the car passed the MOT fine, a few unrelated advisories but with the EML dutifully lighting then going off ;) the emissions test was ok, ( I did use Wynne's Pre MOT fuel additive and a long run after), I suspect that maybe the aftermarket 02 sensors a bit over eager in triggering codes. Car runs superbly acheiving average 43 MPG on a run...Thanks for all the advice everyone.
 


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