O2 sensor . Help

[MAURICE THE MARTIAN]

Hi all.
Got a fault code showing the o2 sensor fault.bank 1. after cat.
So the question is would this have any effect on fuel consuption. Mine has started using about 10_12 % more fuel recently.b ut ive been told coz its after the cat it shouldnt effect it.
Thoughts anyone.??
Cheers M

 

[Grumps]

Do you get a hot smell on occasions mate? Mine needs a lambda and occasionally pushes more fuel though than it needs causing the smell.

 

[Stevo7682]

Bank 1 sensor 1 is the pre cat lambda bank 1 sensor 2 is the post cat.
If either lambda faulty it will effect the car as the fuelling will be incorrect causing carbonising to the engine and excess strain on th cat as it tries to deal with it

 

[Stevo7682]

@Grumpy would i not be right in thinking that your zed has cat test issues.
Lambda fault not going to be doing you any favours there.

 

[billz]

On our 3.0si Bank 1 is Cylinders 1 to 3. Bank 2 is cylinders 4 to 6 there will be both pre and after cat sensors. I know this as i had to have Bank 1 after cat changed 2 months ago. So i would assume yours is the same Maurice. Not sure if it will have a bearing on fuel but i would presume it will affect something unless it is just a monitoring sensor

 

[billz]

Just checked on realoem and yours is the same set up as mine you have 4 sensors 2 are called REGULATING LAMBDA PROBE which sit before the cat and the other 2 are called Lambda Monitor sensor and fit after the cats, so if they are just Monitors then i would assume that is all they will do and would not affect the fuelling

 

[Stevo7682]

Sorry @billz you are right the sixes have 4 lamda 2 cats as you said bank 1 sensor 1 and 2 is cyl 1 to 3 pre and post cat and bank 2 sensor 1 and 2 is cyl 4 to 6 pre and post cat.
The problem will be less noticeable on th 6 cyl but cyl 1 to 3 will not be performing 100 per cent as the sensor will tell fuel computer that either rich or lean and fuelling will get altered

 

[MAURICE THE MARTIAN]

Bloody confusing innit.
Wheres the oracle ttony

 

[Redline]

Hi all.
Got a fault code showing the o2 sensor fault.bank 1. after cat.
So the question is would this have any effect on fuel consuption. Mine has started using about 10_12 % more fuel recently.b ut ive been told coz its after the cat it shouldnt effect it.
Thoughts anyone.??
Cheers M

The obvious point is if the sensor doesn't have any impact if it fails then there's no point in having it.

It's likely to have a detrimental effect to some degree or other and increased fuel consumption/over fuelling is most likely but as just said only on three cylinders. Don't really want it over fuelling as that may damage the Cat. The greater the over fuelling the greater reduction in O2 sensor feedback, reduced Cat operating temperature and so it goes. The electronics have a wide latitude of operation so can map out problems to a degree (to cope with varying fuel quality etc) so that performance doesn't appear to be affected, but, it may be operating well away from the optimal position. I'd suggest getting it looked at rather than ignore the problem. The costs could escalate quickly.

 

[billz]

I was not sure if it would adjust anything but even the monitor sensors i would assume will scrutinise he gases coming out the cats and you would also assume this in turn will tell the computer to adjust something ro get the gases right

 

[Redline]

I was not sure if it would adjust anything but even the monitor sensors i would assume will scrutinise he gases coming out the cats and you would also assume this in turn will tell the computer to adjust something ro get the gases right

It's exactly that. Any feedback system is used to control the inputs. If the sensor isn't working and providing the correct feedback to the control inputs, you have an open loop feed forward system (infinite gain and instability) or at best incorrect outputs.
In the fuelling this will be too little or too much fuel for any given Rev/load map. If the fuel doesn't get properly burnt it will get passed through to the hot cat and potentially burn there instead but without oxygen it will not properly burn and leave carbon and stop the cat from working.
What I don't know is how the ecu knows that the sensor is failing/failed. There must be some differential measurements (comparing the input conditions against the expected outputs) or current sensing on the sensor itself.

 

[billz]

I would assume that because the ECU knows exactly what Modules and Sensors are fitted it will also have an internal Monitor to see if anything goes missing. A bit like fire alarms when a device goes off line.

 

[MAURICE THE MARTIAN]

Just to confuse a bit more, the cats under the car were removed 4 yrs ago, so the car has only the two cats which I think are on or near the manifold,
Could never understand why uk cars have 4 cats yet the American market ones only have the two fitted.
The increase fuel consumption happened overnight so as to speak and has stayed at 10- 12 % worse.
So from the comments a new sensor is needed methinks,
Good discussion aint it, clear as mud to me , ha ha.
M

 

[billz]

The cats still on the car are the main cats that have the sendors on and these are the ones that monitor the gases. The others are just secondry cats more or less they are just eesinators.

 

[billz]

Anyway told you when you told me about the sensor that you need one. Stop being a tight a--e and get one

 

[t-tony]

Sorry late to the party. The post cat sensor are there to make sure the cats are doing their jobs and this is managed by the pre cat seniors. If the post car senior has failed it can deceive the ECU into thinking that the pre cat sensor is not keeping the fuelling to the correct level and may be over fuelling resulting in higher MPG.

Tony.

 

[MAURICE THE MARTIAN]

Cheers Tony, so the consensus is I need a new sensor,
Int this forum great
M

 

[MAURICE THE MARTIAN]

Anyway told you when you told me about the sensor that you need one. Stop being a tight a--e and get one

Who u callin a tight arrrrrr,, just spent a fortune on another motor to replace the vert you lot ruined on hol,

 

[oldcarman]

Do tell @MAURICE THE MARTIAN !! JIM