[Womble]

OK, not really smallholding related but this is driving me round the bend!!

The check engine light on my wee Skoda Fabia came up the other day, so I borrowed a tester from a friend, which came up with "P0141, O2 sensor heater circuit malfunction, Bank 1 Sensor 2".

Since the exhaust had only just been replaced, I assumed that they'd damaged the lambda sensor in the process, so bought a new one, fitted with much swearing. However, the fault has now returned, and has been joined by a friend; "P0136, O2 sensor circuit malfunction".

The sensor is a standard 4-wire job - black, grey, white, white, and it was the rear one I replaced, half way down the exhaust pipe. I've checked the wiring from the car, and I am getting 12V across the two white heater wires. The engine still seems to run fine.

The only thing I'm unsure about is that I'm NOT getting any continuity between the grey (sensor ground) wire and the bodywork. However, if that's a permanent ground, surely there should be continuity there, right?

Any ideas folks?  This one has really got me scratching my head! 

[mab]

TBH you've already gone beyond my knowledge of modern engine electrcs; the only thought I had was if the sensor grounds through the exhaust pipe, but the pipe was too well painted before installation? Otherwise I can only suggest rechecking all the engine electric connectors in case one hasn't been reconnected somewhere.
Good luck.

[Rupert the bear]

did you clear the faults on the ecm ?

[Womble]

Thanks both,


The four wire sensor has its own ground, not via the exhaust pipe, but I did check continuity between the sensor body and the exhaust / chassis anyway, and it was fine.


Yes, I cleared the faults each time. Strangely though, I've just driven 50 miles without any errors coming up, so maybe it's an intermittent fault. We're going down to Englandshire tomorrow; I wonder how far we'll get before the light comes on!

[cloddopper]

Much is talked about getting the vehicle running in regeneration mode .. It involves getting the engine to full working temperature and driving for 50  miles or so at 50 to 70 mph in one go . it cleans the catalyst and burns off any carbon , you engine management system recognises what been done and adjusts things accordingly ,. then the various lights go off. .

This has truly annoyed me several times the last one with light & warnings coming on after  being a six week long  holiday,  towing the caravan , the final leg was us driving back from Southampton and parking the car up .  Getting a cup of tea then unloading the caravan . On detaching the thing we wanted to go shopping , on turning the engine on all the various engine management lights came on & stayed on and on checking in the hand book it says the car needs to be taken to the dealer for attention . I give them a ring and they say bring it straight in.

 18 miles later the dealership guys say " Oh it needs to be put through the regeneration to reset the sensors you haven't been driving it enough .. they dropped their smirks & jaws when I told them the sort of idiots I thought they were as I told them I'd just finished a two thousand three hundred trip , mainly towing the caravan and doing 150 miles just over an hour ago  mainly on the motorway at 60 mph .
 

[Q]

Its not high enough revs to cause a regeneration at those speeds. 
On my car it needs to be a steady speed for more than 20 mins at over 2000 revs.  I don't get above 2000 revs even cruising on the motorway at 70.

I have just paid halfords £99 to force the regeneration thinking they had a fancy bit of computer gadgetry but its nothing special - just runs the engine at high revs.
They also recommend changing the oil afterwards (included in the £99)

[cloddopper]

That's interesting Q , with the KIA Sedona being an automatic there was  no chance of it happening if we hadn't been towing but we often dragged the car down a couple  of gears as there are numerous long slow hills between here & Southampton . Perhaps they weren't so steep or long enough .

I wonder what they did at the KIA dealership , stuck a concrete block on the accelerator whilst the engine was running for about twenty five minutes later that rang us to say it was now OK and they woiuld come to the super market close by to collect us  ?
 

[Q]

There's quite a few youtube videos

this one shows you the way the garage does it.   https://www.youtube.com/watch?v=Dg7kFnNwNCk

[Womble]

Much is talked about getting the vehicle running in regeneration mode ..

Isn't that just for diesels with a (DPF) particulate filter though?


I'm still toiling with mine. If the light comes on, it's almost always 3 miles after starting the journey. If it doesn't come on within that time, I can go indefinitely without it coming up.

I'm going to trace all the wiring back, and also cut the plug off the sensor and solder it direct. If that doesn't fix it, I'm going to stick a piece of black insulating tape over the warning light, and consider it fixed!!

[bazzais]

As ions flow from - to +  I'd put a new earth wire on it, direct to the battery and see if that works.

[cloddopper]

Much is talked about getting the vehicle running in regeneration mode ..

Isn't that just for diesels with a (DPF) particulate filter though?

 Thanks , I didn't realise it was applicable to just diesels .

I'm still toiling with mine. If the light comes on, it's almost always 3 miles after starting the journey. If it doesn't come on within that time, I can go indefinitely without it coming up.

I'm going to trace all the wiring back, and also cut the plug off the sensor and solder it direct. If that doesn't fix it, I'm going to stick a piece of black insulating tape over the warning light, and consider it fixed!!

[regen]

We have a 56 plate Corsa. had it from new and EMS light first came on at about 50,000 miles about 5 years ago and then periodically to 70,000 miles about 3 years ago. Now done 90,000 miles and has come on frequently for last 3 years. two garages have failed to solve it but car keeps going so reckon the black tape could be the answer!

Regen

[Womble]

Thanks , I didn't realise it was applicable to just diesels.

I'm no expert Cloddopper, but I believe that's correct.


More information from the AA here:

If you're buying a new car and plan to use it mainly for town-based, stop/start driving it would be wise to avoid a diesel car fitted with a Diesel Particulate Filter (DPF) because of the possible hassle of incomplete 'DPF regeneration'.

Bazzais - thanks for that tip. I haven't been able to track down a wiring diagram yet, but if the sensor ground is indeed a permanent chassis ground, I agree, that has to be worth one last try before sticking tape over it and pretending it's not there!

[bazzais]

or a relay? maybe?

[Womble]

Well......indications were that the root cause was some sort of intermittent electrical fault, so I chopped off the plug and socket and soldered all the connections directly, as well as running an additional wire to earth as per bazzais' suggestion.


One week on and the fault hasn't come back, so it seems that's fixed it. Thanks everybody!