Hello,
I have a 2007 Nissan Altima w/ 133k miles. Smog/Registration is due soon but my car is 50/50 on passing. I have a Blue Driver, under Mode 6 I'm getting a red "x" for Lean To Rich Threshold Voltage. Every things else is checked green. What could be the issue for this? What is the difference between Rich to Lean & Lean to Rich? How can I accurately read the data?
Thanks
When you run the Bluedriver Smog Check function does your Altima pass?
Mode 6 can be useful but remember, you're looking at a single event(s) or tests which were "noted" by the computer for incorporation into other tests and for reference.
It's like you're peeking over the computer's shoulder and looking at its notes.
Sometimes it can be very useful, sometimes not.
Probably the best example is the cylinder misfire counter.
Let's say your car is running great, no codes either.
You start poking around Mode 6, find the misfire counter and start going through each individual cylinder.
Let's say you find 0 misfires on #1, #3, and #4 cylinders.
Then you see that 1 misfire was recorded on #2 cylinder.
You would be insane to start trying to run down the reason that 1 misfire was recorded on #2 cylinder at a single event over the span of 100's of thousands of engine rpms.
Your car doesn't have a problem.
However, let's say your car isn't running all that great at all rpm ranges. It's not throwing any codes.
But when you go to your misfire counter you see 400 misfires occurred on that #2 cylinder,
Well that's very useful information and you would start investigating what's causing that.
In your case the computer is testing at which voltages (from the O2 sensor) the fuel mixture gets switched.
It tests the voltage value when going from a Rich to Lean condition
and it tests the voltage value when going from a Lean to Rich condition. (only 2 of the many O2 sensor tests)
It found that the voltage value was out of the programmed threshold going from Lean to Rich.
But it's not saying that this is a continuous issue or that anything is wrong.
If it were mad at a particular O2 sensor because of repeated "out of spec" performance issues it would throw a code.
So I don't know if you have a 4 cylinder or 6 cylinder Altima.
If you were to "tap" on that TID (Test ID) on your Bluedriver for "Lean To Rich Threshold Voltage" it should give you the CID (Component ID) for exactly which O2 sensor it's referring to.
I guess if you're the worrying type, you could just change that O2 sensor, but it's probably a waste of money.
There's probably nothing wrong with it.
If you're interested in Mode 6 then you might want to watch a seminar by Doc Nall.
It's a good way to "wade into" Mode 6 data to wrap your head around it.
https://www.youtube.com/watch?v=opSsKcKkxf8
Thank you! I appreciate you taking time to explain this. Yes it passes from time to time. I have had the S.E.S illuminated in the past with a P0420 Code. It will illuminate if I change where I fuel up. My Altima perfers Chevron. Once I fuel up with Chevron and drive around a bit it will clear. I run the smog check a few times in the days after and it goes from yellow to green but I notice the red "x" is always there.
This last instance I fueled up with Chevron but I had added fuel system cleaner this time around because I never switched from Chevron since I last got the code.
I'm just trying to avoid damaging my cat. I'll change 02 sensors if I must but I'd prefer to narrow it down. A P0420 code could be many things.
I would be more concerned about any codes stored than what the scanner is showing.. as long as your not tripping any lean or rich codes then the vehicle is operating as it should. The whole job of the air fuel and oxygen sensors is to switch back and forth rich to lean in order to try and maintain ideal air fuel ratios
