Technical O2 sensor 2 bank 1

[12[X]]

Hopefully a quick easy one :yum:. Been suffering poor idle (lumpy? feels like occasional misfires but not as strong as a misfire and no error codes ). Been trying to figure this out for a very very long time (a year or 2) but being really stupid when it comes to electrical systems doesn’t help much :bang: Was having another look at live lamda readings today.. sensor 1 bank 1 seems OK changes rapidly between ≈.1 V and ≈ .8 V same goes for sensor 1 bank 2... However... sensor 2 bank 1 is a flat reading of 0.310 V ... This is post cat? Surely it cannot cause all my troubles ?! As always many thanks for replies

 

[NumanR]

Lambda sensors post cat normally give a straight signal at idle, if you rev the engine up the sensor signal will change, pre cat the sensor signal switches, post cat it doesnt because the cat uses the oxygen in the exhaust. You have to introduce extra oxygen by revving and releasing the throttle to test the post cat sensor properly. Post cat sensors do not cause misfires, they are only used to test the catalytic converters efficiency.

 

[Davren]

Think there may be something wrong with your diagnostic. You would only have a bank 2 sensor if you have a V engine.

 

[12[X]]

thank you, looks like back to square 1 (and no error codes apart for P1531.. will go get a new air con relay in a few days) damn it bet it is something really stupid! (perhaps the fuze box got wet at some point?! this damn thing started after a clutch failure)

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there are 3 sensors and only 3 feeds - the software might be off with naming but not the signal?!

 

[Davren]

there are 3 sensors and only 3 feeds - the software might be off with naming but not the signal?!

Just thought..... if you have the 1.8 engine, bank 1 and bank 2 could refer to the 2 pre cat lambda sensors on the twin cat down pipe. But they should both be showing the same reading.

 

[12[X]]

yep its a 1.8 but 2 pre cats won't have an identical reading as they respond to a pair of cylinders each.. having said that i get your point - there is no way of knowing if the flat reading is coming from a post-cat or a pre-cat sensor.. got some more software to try tomorrow (and this one lists all the sensors as bank 1.. still which is which is a guess?! Am currently guessing that 1 is cyl 1+2 2 is cyl 3+4 and 3 is post-cat) any free elm scan 5 software recommendations anyone?

 

[12[X]]

Ok tried 3 different software titles.. all with same results bank 1: two sensors bank2: 1 sensor. Am guessing that Fiat config is different from GM . Anyhow.. am also guessing that bank 1 sensor 1 is cylinders 1&2 pre-cat, bank 1 sensor 2 is post-cat and bank 2 sensor 1 is cylinders 3&4 pre-cat. Pic attached, unfortunately i’m way too inexperienced to see if there is a problem – be much appreciated if someone could take a look (as it all looks fine to me )..

Although I’ve another avenue to investigate now.. Starting from yesterday been getting fuel level sensor connection faults on startup from warm.. this being one unit with the pump it is feasible that there are fuel pressure variations causing my idling issues?!