Help, I'm trying to diagnose whats wrong here. Ive plugged in the VCDS and here is the screen shot of the fault codes and a pic of the O2 sensor.

I've tested for a supply to the heater and a supply to the sensor and these are fine. Also the resistance of the heater seems ok.

There is a grey/brown deposit on the sensor, but its not thick and Im not sure whether this could affect its operation.

 

Do I just replace the sensor? or could it be something else?

 

Thanks for looking.

 

Ideally you want to test the continuity of the heater connection to the ECU. Can tell you wire colour and pin numbers if needed.

Ok, I can see on the wiring diagram - it looks like a brown wire from terminal 2 on the socket - not sure how to find it at the ecu though.

 

Nice to talk again!

Ah it looks like that wire runs to connection is no4 on the 81 pin connector at the ecu - this could be fun!

Yep, pin 4 of ECU connector.

 

Your 16825 code points to a purge valve fault (or wiring to it), I think. Check that wiring too if poss.

 

 

Edited 29 May, 20179 yr by Wino

Great, what does the purge valve do?

Connects the charcoal canister to the intake as and when, and to the degree that the ECU sees fit. Basically deals with fuel tank emissions. 

Ok thanks for that - Ill keep you posted

Bet the O2 sensor is goosed, try soaking it in white vinegar to clean it up, failing that just replace it then clear all the codes.

All petrol Fabias I've seen so far throw the purge valve code at some point in their life, clear it and ignore it, it's not affecting your emissions.

Well its p$%ing down atm so no progress til tomorrow chaps - thanks for your input

How much did it fail by, a bit or a lot?

 

On the 1st fast idle test CO was 0.88% and the limit is 0.3%. Lamda 0.982. HC 70 ppm.

On the 2nd fast idle test CO was 1.05% and the limit is 0.3%. Lamda 0.974. HC 28 ppm.

On the natural idle test CO was 0.39% and the limit is 0.5%.

 

What do you think?

Just whipped the plugs out so here they are cyl 1-3 left to right. No. 1 smelt strongly of fuel (faulty injector?) but otherwise they would clean up.

 

Not sure what all the deposits on no 3 mean?

 

I also checked the heater wire back to the ecu and there was continuity so all looks good there.

Forgot picture!

Hmmm, I say treat it to a new set of plugs - if numbered from left to right, that number three is gone. Interesting that number one stank of fuel, the colour looks reasonable. Is there any misfiring evident? 

Number 3 is a completely different spark plug to the other two, different grade and brand. Replace with a new set, all the same, doesn't matter what brand they are as long as they're the correct plug specified for that engine.

Yep replace the plugs as a set, i'd change the lambda sensor's  as well (always two on obd systems). Normally high co readings at fast idle points to lambda sensors being out of wack. Try also to fit genuine items as aftermarket items tend to only last a few months.

Edited 30 May, 20179 yr by Ju1ian1001

2 minutes ago, Ju1ian1001 said:

Yep replace the plugs as a set, i'd change the lambda sensor's  as well (always two on obd systems). Normally high co readings and fast idle points to lambda sensors being out of wack. Try also to fit genuine items as aftermarket items tend to only last a few months.

 

Good advice although I always use NGK plugs and probes rather than OEM stuff, I'm not a brand fairy it's just that NGK seem to have superior QA systems to anyone else because I've never had a duffer in 35 years of using their stuff in every type of engine you can imagine.

2 minutes ago, sepulchrave said:

 

Good advice although I always use NGK plugs and probes rather than OEM stuff, I'm not a brand fairy it's just that NGK seem to have superior QA systems to anyone else because I've never had a duffer in 35 years of using their stuff in every type of engine you can imagine.

 

The only engine i have found that didn't like NGK plugs was a rover V8, did part of my apprenticeship working on range rover classic's and MK1 discovery's, if we fitted NGK's they would cough and splutter all over the place, fit a set of champion plugs and they ran sweet as a nut.

Thanks for the advice - Ive put new ngk plugs in, but going to let the garage try new sensors if that turns out to be the problem. The garage said it was misfiring but I couldnt detect it. 

 

Those plugs pictured are all ngk btw, its just that last one is covered in crud! Am worried its oil which means this CO issue may not go away easily.

 

Its going for retest tomorrow so will report back.

13 minutes ago, gareth29 said:

Thanks for the advice - Ive put new ngk plugs in, but going to let the garage try new sensors if that turns out to be the problem. The garage said it was misfiring but I couldnt detect it. 

 

Those plugs pictured are all ngk btw, its just that last one is covered in crud! Am worried its oil which means this CO issue may not go away easily.

 

Its going for retest tomorrow so will report back.

 

Nah, HC would be WAY up if it were burning oil, it does look like that number 3 plug has been misfiring and running cold which is why I thought it was a different colder plug.

 

CO is mostly caused by poor combustion from a dodgy plug or coil pack.

Or the cat is fu_ _ed..

22 minutes ago, w.t100 said:

Or the cat is fu_ _ed..

 

CO is believe or not too high for the cat to be knackerd. A knackerd cat usually gives a CO reading of 0.50 at fast idle and usually stays at that point or just above, anything higher then this then point to lambda or some other sensor as the cars ECU will default to over fueling.

 

Burnt/worn out coils packs or spark plugs and burning oil lead to the HC's being high and can sometimes cause higher CO.

Interesting reading - my logic was that its not going to cost me much more if they replace the sensor or i do it - Id just be gambling.

 

Is your engine definitely an AWY, not a BMD code?

I tried to look up the appropriate VAG part number for your pre-cat lambda sensor here (one of the first two item 12s), based on the VIN/chassis number in your scan picture, and it looks like AWYs were only fitted up to chassis number 6Y-4-095989, and yours is 6Y-4-967534? As I understand it, characters 9 and 11 get replaced by dashes to generate the chassis number from VIN in the form that ETKA shows them.