Bank 2 O2S bad?
Bank 2 O2S bad? Hey guys. My car started running terrible today. missing very badly, felt like it was only running on one bank. Well, it basically is only running on bank 1. I plugged up to the diagnostics and these are my results. No faults codes oddly.....
Bank 1 O2 sensor voltage is fluctuating normally between .2 and .8 Volts
Bank 2 O2 sensor is flat lining anywhere from .9 - 1.1 Volts
Bank 1 short term fuel trim: -1.6 %
Bank 2 short term fuel trim: -39.1 % woah!
Bank 1 long term: 8.6 %
Bank 2 long term: -10.6%
I believe the Bank 2 O2 sensor is taking a ****. Bear in mind that my car runs perfectly fine when it is in open loop. Once it goes in to closed loop and starts lookin at the O2 sensors.....then it runs like ****. Because of this it hard to believe that it could be any kind of fuel issue or anything thats not PCM controlled. I have checked fuel pressures...Good.
So how do yall feel about my diagnosis? Please provide any input. Thanks
Bank 1 O2 sensor voltage is fluctuating normally between .2 and .8 Volts
Bank 2 O2 sensor is flat lining anywhere from .9 - 1.1 Volts
Bank 1 short term fuel trim: -1.6 %
Bank 2 short term fuel trim: -39.1 % woah!
Bank 1 long term: 8.6 %
Bank 2 long term: -10.6%
I believe the Bank 2 O2 sensor is taking a ****. Bear in mind that my car runs perfectly fine when it is in open loop. Once it goes in to closed loop and starts lookin at the O2 sensors.....then it runs like ****. Because of this it hard to believe that it could be any kind of fuel issue or anything thats not PCM controlled. I have checked fuel pressures...Good.
So how do yall feel about my diagnosis? Please provide any input. Thanks
Registered User
Joined: Nov 2008
Posts: 2
Likes: 0
O2 sensors do not normally fail to the high (rich) side.
I would be looking for something like an injector or
injector harness fault, something that is shooting a
whole lot of excess fuel. Could be as little as a weep
if the bank looks real bad at idle but cleans up at a
higher RPM. Maybe start with the easy thing, which
is probing the average voltage across the passenger's
side injectors (DMM and a pair of needles) to see if
any difference onone or the gang, exists relative to
driver's (OK) side. If no electrical difference then go
on to something like a bank-bank swap of injectors
(in an orderly way so when a bad boy moves you
can see it right off).
I would be looking for something like an injector or
injector harness fault, something that is shooting a
whole lot of excess fuel. Could be as little as a weep
if the bank looks real bad at idle but cleans up at a
higher RPM. Maybe start with the easy thing, which
is probing the average voltage across the passenger's
side injectors (DMM and a pair of needles) to see if
any difference onone or the gang, exists relative to
driver's (OK) side. If no electrical difference then go
on to something like a bank-bank swap of injectors
(in an orderly way so when a bad boy moves you
can see it right off).
Well like I said, It runs perfectly fine in open loop. Once it goes into closed loop and starts looking at the 02sensors, then it runs like ****. Which is why its gotta be a pcm controlled/monitored issue. Ill try swapping the O2s between banks and see was happens.
The thing with closed loop is, when you have an
unbalanced injector delivery the trimming will work
to balance the sum. One injector at +40% (140%)
and three at 100%, will trim down until you have one
at 1 at 130% (11:1) and three at 90% (16:1). Motor
is a lot more tolerant of rich, than lean. Hence "OK"
open loop and stumbling bad in closed loop.
Just a theory.
unbalanced injector delivery the trimming will work
to balance the sum. One injector at +40% (140%)
and three at 100%, will trim down until you have one
at 1 at 130% (11:1) and three at 90% (16:1). Motor
is a lot more tolerant of rich, than lean. Hence "OK"
open loop and stumbling bad in closed loop.
Just a theory.
