O2 Sensor Readings Ok?
Thread Starter
Teching In
Joined: Oct 2008
Posts: 9
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O2 Sensor Readings Ok? Cammed ect LS1 in a 3rd gen, no rear O2s. Has a base tune to get it running, but trying to make sure I'm not having any other issues before I take it in for a dyno tune. The V is within range, but not sure why one bank is 5x the other or why my STFT on the same side is 10x. Or where the V register for the S2's is coming from? B2 S1 should read about .155, number was changing when I took the pic. They are fluctuating but stay around this same range. One bank seems to be running about 60 degrees hotter, but that could be from more cool air on one side. 5 codes are coming up but my cheapy scanner won't let me scan past the no fan signal code.
The trims don't work on voltage per se, but on time above
and below threshold (nominally 500mV but the actual trip
level ranges from 350 to 450mV in tunes I've seen).
If the switching waveform is fast and balanced then a
445mV reading as seen here is pretty right (if you have
a tune that wants 450mV, that's a trivial error voltage
and about as good as it gets).
An average of 150mV means either the sensor is dead-ish,
the fueling is whack (either from air or fuel side or misfire,
air is common to both banks so unlikely). Near-dead sensors
can put out some voltage and deliver some switch events
but may spend most of their time passed out on the floor
waking up only when heavy fuel is shot.
A simple test since you have one sensor working is to
swap them side to side on the pipes, see if the "right
answer" moves with the component (after some time
spent relearning trims) which would indicate the "wrong
answer" lies with the sensor, or stays put (indicating
perhaps a misfire or crusty injector type problem on that
bank). Might look at misfire current cylinder mode on 1-8
to see if anything stands out worth a closer look.
and below threshold (nominally 500mV but the actual trip
level ranges from 350 to 450mV in tunes I've seen).
If the switching waveform is fast and balanced then a
445mV reading as seen here is pretty right (if you have
a tune that wants 450mV, that's a trivial error voltage
and about as good as it gets).
An average of 150mV means either the sensor is dead-ish,
the fueling is whack (either from air or fuel side or misfire,
air is common to both banks so unlikely). Near-dead sensors
can put out some voltage and deliver some switch events
but may spend most of their time passed out on the floor
waking up only when heavy fuel is shot.
A simple test since you have one sensor working is to
swap them side to side on the pipes, see if the "right
answer" moves with the component (after some time
spent relearning trims) which would indicate the "wrong
answer" lies with the sensor, or stays put (indicating
perhaps a misfire or crusty injector type problem on that
bank). Might look at misfire current cylinder mode on 1-8
to see if anything stands out worth a closer look.
Thread Starter
Teching In
Joined: Oct 2008
Posts: 9
Likes: 0
Thanks Jimmy that helps a lot. Fired it up again last night and both rears (that aren't actually there) stay in a range from 440-450, so I'm assuming they just guessed on the base tune as a sweet spot, but sounds like it is fine.
The two front that are actually present appeared to be working correctly now. They jump from 0 up to 150ish and anywhere in between at idle. It is a fresh swap and I have had some misfire from some faulty electrical connectors for my ignition coils. I identified 2 that were definitely fouled that I replaced already, and have ordered the other 6 but waiting on them to come in and wire them up.
From what you are saying I'm going to assume I had a misfire on B2 when it was running with this data log. I'll wait and change all these connectors out and continue looking at the data log to see if one falls asleep again.
Can you switch sensors L and R? I'm showing the same part numbers front and back, but not left and right. I know the left one has a longer wire on the connector. Is that the only difference between the two? Might just put some new ones in anyways, I can get Denso's for $30 ea, and these did look like they had a few miles on them.
The two front that are actually present appeared to be working correctly now. They jump from 0 up to 150ish and anywhere in between at idle. It is a fresh swap and I have had some misfire from some faulty electrical connectors for my ignition coils. I identified 2 that were definitely fouled that I replaced already, and have ordered the other 6 but waiting on them to come in and wire them up.
From what you are saying I'm going to assume I had a misfire on B2 when it was running with this data log. I'll wait and change all these connectors out and continue looking at the data log to see if one falls asleep again.
Can you switch sensors L and R? I'm showing the same part numbers front and back, but not left and right. I know the left one has a longer wire on the connector. Is that the only difference between the two? Might just put some new ones in anyways, I can get Denso's for $30 ea, and these did look like they had a few miles on them.
On my Camaro and my Vortec van, fronts are same for
both sides (inline-4 connector) and rears are same side-
side but different from fronts with a 2x2 connector.
Corvette rears are like Camaro fronts but with about
2' of harness, nice for headers (well, as nice as any
O2 sensor can be in too cold of a pipe). And that's
another variable, especially as sensors age they do
worse and worse when underheated (like at idle in
a big-*** heat-shedding header collector). Every
late fall, the "O2 sensors not working, idle sucks"
threads return like clockwork....
both sides (inline-4 connector) and rears are same side-
side but different from fronts with a 2x2 connector.
Corvette rears are like Camaro fronts but with about
2' of harness, nice for headers (well, as nice as any
O2 sensor can be in too cold of a pipe). And that's
another variable, especially as sensors age they do
worse and worse when underheated (like at idle in
a big-*** heat-shedding header collector). Every
late fall, the "O2 sensors not working, idle sucks"
threads return like clockwork....
