Technical Changing Lambda sensors

[Tony123]

forgive me if this sounds stupid...
i want to change the lambda sensor on my HGT punto
The sensor which comes up as a faulty one is
Oxygen sensor 2 on bank 1
this also throws off oxygen sensor 1 on bank 2

can any tell me which sensors are which please.
I know were all 3 are,
i can see one to the left of the manifold and one on the right of the manifold then there is one that i think is going to the back of the cat ?

reason for me chaning is obv because its coming up on the diag reader, but also when i put my foot down the car lags as if theres too much fuel going in and this is the last thing i can think of to change.

 

[SamuraiDragon]

more often than not, i believe the pre cats cause the most problems from faulty sensors. my 1.2 16v has 2 sensors so not really sure on the third. id take a wild guess that its one of the 1st 2... the post cat sensor isnt much of a problem creator so ive heard.

 

[Tony123]

any idea what would cause my car to act like theres too much fuel going in ?
When i put me foot down i get acceleration then after certain revs is hesitates and slows down.

Would a too tight belt do this ?
either cam or aux belt ?

 

[wilko92]

do you get back fire and misfire? if so new spark plugs.. happends to me and it bassicaly said my car was fked on the code reading.. new spark plugs cleared the ecu and was fine after that!

 

[Tony123]

Nah no back fire or mis fire, I've got new sparks, new fuel injectors,
Could the cat be ****ed?

 

[MikeSalt]

Tony,

Long shot here, but did you identify which sensor 2, bank 1 was? If it was pre-cat, was it timing belt side or thermostat side?

Cheers,

Mick

 

[MikeSalt]

Tony,

I did some diagnostics last night by pulling wires and using MultiECUScan. Answers are here.

Cheers,

Mick

 

[fingers99]

It would be logical for a fault with a pre-cat to trigger the post cat: the post cat basically monitors whether the pre cats are working properly.

Good post by Mike.

 

[MikeSalt]

It would be logical for a fault with a pre-cat to trigger the post cat: the post cat basically monitors whether the pre cats are working properly.

I agree with that logic. With a failing pre-cat sensor, the closed-loop feedback system simply doesn't work, leading to improper fuelling on the cylinders it is attached to. Being downstream of the pre-cat sensors, the post-cat (Bank 1 Sensor 2) sensor will also pick this up. The main function of the post-cat sensor is to just verify the efficiency of the catalytic converter. I suspect that the sensor that needs replacing is Bank 2 Sensor 1, which is the pre-cat sensor for cylinders 3 & 4. With this replaced, the closed-loop feedback system should work properly again and the readings by the post-cat sensor should return to normal. It might need a bit of a run though and then clear the codes.

 

[MikeSalt]

Does anybody know where the plug for the post-cat sensor is located? The cable is over 1.3m long, and disappears behind the exhaust heat-shielding so without getting the car on axle stands, I cannot really follow it. I'm hoping for a dry day so I can crawl about on the floor soon though, not going to buy a new sensor until I've inspected all the wiring.