Lean Code and 02 Code diagnostics.

[Kiske]

Does anyone know off the top of their head where B1 Sensor 2 is located on the factory exhaust? I'm thinking this is the one after the cat on the oem header. Can anyone confirm this. I've got a p0140 coming and going only staying on for 2-3min at a time before clearing on it's own.

Just wanted to get an idea so I can grab a sensor on my way home after work before the dealer closes incase it isn't a simple wiring fix. Thanks.

[Poodles]

Yes, it's the one after the cat.

[tskaohu]

yes that is on the stock header after the cat. if you got a p0140 coming on and off its most likely a bad sensor, damaged by water or even melted. new sensor should clear it all up. but if it doesn't, disabling the code in your tune is the best thing to do. doesn't affect driveability just monitoring the efficiency of the cat. Pretty much always disabled if you get non factory headers aha.

[steve99]

Originally Posted by Kiske

Does anyone know off the top of their head where B1 Sensor 2 is located on the factory exhaust? I'm thinking this is the one after the cat on the oem header. Can anyone confirm this. I've got a p0140 coming and going only staying on for 2-3min at a time before clearing on it's own.

Just wanted to get an idea so I can grab a sensor on my way home after work before the dealer closes incase it isn't a simple wiring fix. Thanks.

do you have flex fuel kit ? that uses rear 02 as input ? if so tuner should have disabled it in tune.


If you can log the rear o2 sensor readings if its still in use


The rear 02 also does cruise fueling adjustments and can cause some weird stuff to happen if its not disabled correctly in tune ie its more than just disabling P0420.

[tskaohu]

@steve99 to the rescue^^^ the man with the know how aha

[Kiske]

Originally Posted by steve99

do you have flex fuel kit ? that uses rear 02 as input ? if so tuner should have disabled it in tune.


If you can log the rear o2 sensor readings if its still in use


The rear 02 also does cruise fueling adjustments and can cause some weird stuff to happen if its not disabled correctly in tune ie its more than just disabling P0420.

Nah no flex fuel, but B1 and B2 are mounted right next to eachother on my turbo kit's downpipe. I completely forgot we didn't have a seperate banks.

I've yet to get the code to come back. I did monitor the rear o2's voltage and it seems low. 0.045v where the front 02 sensor is around 1.0v

I cannot see frying my rear 02 without taking the front 02 sensor with it because they are litterally side-by-side. I think I'll do a cold reset next so my car can relearn. This code popped up just after fixing a lean code (p0171) and replacing manifold gaskets.

[steve99]

Originally Posted by Kiske

Nah no flex fuel, but B1 and B2 are mounted right next to eachother on my turbo kit's downpipe. I completely forgot we didn't have a seperate banks.

I've yet to get the code to come back. I did monitor the rear o2's voltage and it seems low. 0.045v where the front 02 sensor is around 1.0v

I cannot see frying my rear 02 without taking the front 02 sensor with it because they are litterally side-by-side. I think I'll do a cold reset next so my car can relearn. This code popped up just after fixing a lean code (p0171) and replacing manifold gaskets.

You should get some movement in the rear 02 sensor volts (its only a narrow band sensor) as you cruise/accelerate/off throttle if its just stuck at one level then is suggests something wrong with wiring or sensor. Maybe unplug sensor and see if volts change as well .


If you had to use a lot of force to install or remove it can damage them maybe run a thread tap though the exhaust bung if it was tight so if you buy a new one is not damaged.

[Sportsguy83]

Originally Posted by Kiske

Nah no flex fuel, but B1 and B2 are mounted right next to eachother on my turbo kit's downpipe. I completely forgot we didn't have a seperate banks.

I've yet to get the code to come back. I did monitor the rear o2's voltage and it seems low. 0.045v where the front 02 sensor is around 1.0v

I cannot see frying my rear 02 without taking the front 02 sensor with it because they are litterally side-by-side. I think I'll do a cold reset next so my car can relearn. This code popped up just after fixing a lean code (p0171) and replacing manifold gaskets.

I may have missed it, but do you still have a Cat? It seems you don't (turbo kit downpipe) and the code is coming up because of it. The rear O2 monitors Cat efficiency. Need to turn the code off in the tune.

[Kiske]

I've no cat, nor have ran one in 2years. I've never had the code so I'm sure it is correctly disabled. This is a fresh problem that may be much larger than I thought and related to a previous issue I've yet to wrap my head around.


If you want the full problem/diag story and think it would help.

Around a week ago I noticed a bit of hesitation/flutter when lightly on the throttle, holding steady highway cruising. 6th gear, 3500rpms, barely on the throttle, the car would buck, or flutter a bit. This could be remedied by giving it more gas or backing off the throttle. During this occurance I wouldn't be in boost, and my gauge would be around -3 inhg. This was a very rare occurance. Maybe once in a 20 mile round trip.

I've had this happen before. We found the culprit last time to be the under intake hoses leaking. This time I pulled the intake, blocked it off and did a boost leak test. I squirt the hoses and joints with soapy water and gave it a bit of pressure. Probably around 2lbs. I quickly noticed the o-ring around the mas air flow sensor bubbling. I found a replacement o-ring and gave it a light smear of black rtv around the outside of the sensor to air in the seal.

White the rtv was curing I started going after and exhaust leak I heard earlier. I found the header was loose. I tightened it and then called in an evening.

The next day I buttoned up the intake, fired it up and checked for the exhaust leak, all happy. Drove it home, everything sounded great and it ran perfectly.

The next morning I fired it up and drove to work. No issues. Popped a cell p0171 (lean) p0140 p1171 (direct injector issue.) Pulled in into the shop, blocked off the air filter and did a full intake smoke test. No leaks found, hopped under the car and check the header, turbo and downpipe for leaks. All happy. Cleared codes and drove it. The car began to to miss a bit. Watching the misfires, I can see around 5 miss fires on cylinder #2 and a random miss fire on the other 2 cylinders over a 3 min period. Plugs still look brand new (only 30,000 miles.) Checked fuel pressure and voltage to the pump, all happy there.

Rechecked my vacuum lines, filled it up with fresh 93 and drove it home. Still hitting target afr's. Since clearing the codes. I had the p1171 stay off, the lean code comes on and goes and the p0140 had went on and off light a light switch, noticeable by the cruise control and traction control lights flashing on when it is set and clearing when the code is off. Still running a bit lean after looking at my stft/ltft. The car will run, it now just want to stall when the throttle is lightly blipped.

I *hope* for the MAF sensor crapped out on me and as such it is causing the lean code, and in turn causing the p0140 because of crazy readings. Trying to solve while waiting on parts. Swapping an o2 and maf seem like the next step, sadly nobody has them local and it's going to take the dealer around 4 days from when I ordered them... $320 for the maf, $349 for the a/f sensor and $290 I think for the downstream sensor

I find it odd I never set a lean code when the header was loose and now that it is tightened up it shows up.

[Sportsguy83]

Originally Posted by Kiske

I've no cat, nor have ran one in 2years. I've never had the code so I'm sure it is correctly disabled. This is a fresh problem that may be much larger than I thought and related to a previous issue I've yet to wrap my head around.


If you want the full problem/diag story and think it would help.

Interesting... maybe an injector took a crap and thus you're getting the lean code? But that still doesn't explain the P0410 code. That code comes up like Steve said, when using the rear O2 for flex fuel.

[steve99]

P0140 code is no activity from rear 02 sensor
P0420 is the cat efficiency code , this is usually disabled if catless header,manifold used.

If your getiing multiple weird unrelated codes it can be an electrical problem like missing or bad earth straps to engine, or alternator or even a dying battery. All these can cause weird voltage fluctuations whick confuse the ecu when its reading sensors.

but if the rear 02 volts is just stuck on one value it looks very suspect.

[Kiske]

Originally Posted by steve99

P0140 code is no activity from rear 02 sensor
P0420 is the cat efficiency code , this is usually disabled if catless header,manifold used.

If your getiing multiple weird unrelated codes it can be an electrical problem like missing or bad earth straps to engine, or alternator or even a dying battery. All these can cause weird voltage fluctuations whick confuse the ecu when its reading sensors.

but if the rear 02 volts is just stuck on one value it looks very suspect.

Can confirm o2 sensor changes. Ran the car with the maf and both o2's unplugged. I then got them plugged back in. At that time a local buddy let me borrow his MAF sensor in return for buying him lunch. Soon as we fired her up the car imediatly ran better. Through closed loop everything looked great and then I watched the o2 bounce around quite a bit before slowing down to a more steady reading. Even hit stft of 2.1 for quite a while before it maxed out lean (25+.)

I'll continue trying to figure out my lean code in the meantime. Tomorrow I'll start checking the port injectors and o-rings.

I called on the parts to check the DI and everything from the orings to the hard fuel lines is 4 weeks out. I'm doubting it is the direct injectors causing it to lean as the lean code is primarly at idle. Also from what I've read the seal being bad or the injector itself being stuck creates a horrible missfire situation that is easily noticible and seems to make ist very difficult to drive above 5k rpms. I'm hardly missing at all if any at times too.

If I bump up and hold the rpms around 2000 I can watch the STFT get quite a bit better. Which would imply that is is a leak at idle... that even after smoking I cannot find. :/ I guess it could be a leaking valve seal.

[Kiske]

Alright. Rear o2 is working. Still running lean though. After warming up the car I began unplugging the port injectors while running to see if I could get any changes. Sadly it didn't do shit so, I assume it was running off the direct injectors...


Tried again during a cold start and each port injector nearly stalled the engine when unplugged. So dead port injectors is ruled out. :/