technical oxygen sensor problem

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Jun 25, 2009
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This is a little more technical then what I’m used to in a while. My 2005 Infiniti G35x with 71k has been having a on and off CEL for the past month. P1283- Air fuel ratio sensor 1 lean shift- bank2. It comes and goes, like I can drive 100 miles and it would never light up and I can go 15 miles and its always on. Car runs great. MPG seems to drop about .5 MPG but then again its winter blend fuel time. I didn’t see the CEL for almost 2 tanks of gas (300 miles per tank), then I filled up with a tank of Sam’s club gas. Within 10 miles, it was on with the same fault. And it would repeat say every 15-25 miles. I ran down that tank instantly and got to Mobil. Full tanked it on 93 octane, it was good for the first 100 miles and now it’s back again. Here is a kicker, it will set the readiness code almost everytime! So I can still pass emissions in my state pending on time I take it in. I have an android phone with the torque app, so I set it to graph the both front 02 sensors. First thing I see is bank 1 being at 0.3volts and bank2 being at 0.5v. I take it for a drive to watch the voltage to see if I have one of those LAZY sensors. Aside from the difference in voltage I noticed bank 2 would spike up more than bank 1 and in most cases it would hit .9-1.2v and the most bank 1 would hit is .7v, this is me gunning it and letting off. I assume me letting off triggers the lean condition and the higher voltage is leaner and lower voltage is richer. Would it be safe to say I have a soon to be dead bank2 sensor? Is there any testing I can or should do? I always thought .5v was a good idle voltage and not .3v
 
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Greece
Lean condition is low voltage and vice versa. Check your exhaust. You might have a leak before the sensor.
 
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I went through misery with my M35x and this freaking code. I checked for exhaust leaks there were none that i could feel or hear and it would go up to 150 miles without setting the code other times only a few miles. It also ran all the monitors. I checked the wiring, O2 sensors, vacuum leaks, you name it and just about given up. There is a bracket that goes under the transmission and connects to the left and right converters. The darn tab where it connected on the converter is in between the front and rear O2 sensors and one had a very thin tear in it. Only when you hit a bump in the road did the thing open very slightly and let unmetered air in triggering the code. Put the car on ramps, let it go cold the have someone start the engine while you push up on the converters and feel for a leak at the cat mounting tab. You have to be quick about it as they get hot real fast. Once you find it remove the cat and mig weld the tear, i also welded a reinforcing patch around it from heavier stock. Its not rust its a tear so no need to replace the cat but reinforcing it is a must if you want it to last permanently.
 

djb

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Lambda control fault codes are rarely the sensors, they are usually vacuum leaks. The error is the computer complaining that it can't adjust enough to get the sensor to report in-range values. If your car doesn't move, you don't look at the speedometer reading '0' and conclude that the speedometer is broken. That's pretty much the situation here. That doesn't keep auto parts stores and shops from selling a new sensor as part of the remedy, solely because the error code has to do with the sensor's value. The most common causes are on the intake side, a vacuum leak or low fuel pressure / clogged injector. Torque (really, OBD2 over CAN) doesn't sample fast enough for you to conclude that a sensor is end-of-life from slow response. Don't use that as an indication.
 

bowlofturtle

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I know torque isnt the best tool but something can be better then nothing. The different voltage instantly was a little odd. Hopefully i can jack up the car this weekend and find something. I just found it VERY odd that the whole time it was on SAMs club gas it was triped the CEL a lot more VS normal station gas.
 
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Quote:
How does air leak into an exhaust when running?? It can't.
It sure can and when it is in between the front and rear sensors on this car which uses wide bands it causes these exact symptoms. http://www.therangerstation.com/tech_library/O2Sensors.htm
Quote:
6. Exhaust leaks, especially near the sensor can pull in air and cause a false lean reading.
http://www.engine-light-help.com/oxygen-sensor-codes.html
Quote:
A leak in the exhaust system before the O2 sensor will also cause incorrect readings
 
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WatUpDoc
^When I got my 92 VX, it came with a dead original factory wide-band 5-wire. Thankfully, it wasn't hard to remove and I just got a good 1/2 turn once it bottom out to tighten it down. No more CEL. laugh However, the thought of an exhaust leak on the manifold, which is known to happen with these older 4 cylinder civics is worth looking at. Right now I'm trying to find intake/vacuum leaks, though. duh
 
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Originally Posted By: Trav
Quote:
How does air leak into an exhaust when running?? It can't.
It sure can and when it is in between the front and rear sensors on this car which uses wide bands it causes these exact symptoms. http://www.therangerstation.com/tech_library/O2Sensors.htm
Quote:
6. Exhaust leaks, especially near the sensor can pull in air and cause a false lean reading.
http://www.engine-light-help.com/oxygen-sensor-codes.html
Quote:
A leak in the exhaust system before the O2 sensor will also cause incorrect readings
They have it backwards. An exhaust leak is under pressure, and does not admit air into the system. What is possibly happening is that the exhaust leak is affecting the OTHER side of the O2 sensor, which it references off of! It no longer reads ambient air, but exhaust.
 
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Originally Posted By: mechtech2
An exhaust leak is under pressure, and does not admit air into the system.
An exhaust leak can suck in air in very short bursts under certain conditions (such as a misfire or burned exhaust valve http://www.motor.com/magazine/pdfs/042006_05.pdf). It might be possible for these small, short, inward breaths to happen with an exhaust leak for a normally operating engine. I don't really know. The newer Chrysler engines that don't use EGR systems use valve timing tricks to suck back a little bit of the exhaust stream in order to accomplish what the EGR system formerly did.
 
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Originally Posted By: Samilcar
Originally Posted By: mechtech2
An exhaust leak is under pressure, and does not admit air into the system.
An exhaust leak can suck in air in very short bursts under certain conditions (such as a misfire or burned exhaust valve http://www.motor.com/magazine/pdfs/042006_05.pdf). It might be possible for these small, short, inward breaths to happen with an exhaust leak for a normally operating engine. I don't really know. The newer Chrysler engines that don't use EGR systems use valve timing tricks to suck back a little bit of the exhaust stream in order to accomplish what the EGR system formerly did.
A misfire or burned valve is really quite different than normal conditions. And having the engine 'OFF' doesn't count, either!
 
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Valve overlap causes this also.
Quote:
Later intake valve opening can restrict the entry of air/fuel from the manifold and cause in-cylinder pressure to drop as the piston starts to descend after TDC. This can result in EGR if the exhaust valve is still open as gasses may be drawn back into the cylinder
And with it ambient air if there is a leak. Exhaust is only under pressure part of the time, the exhaust is actually a series of pulsations and its these pulsations that allow ambient air to be drawn in through a leak. But there is another simple explanation. Take a air compressor hose coming from the tank and immune from the pulsing cycles of the pistons. It has 100% pressure all the time, now put a blow gun on the end with a siphon tube, what happens? It draws through the siphon tube and with it the cleaner, paint or what have you. Now create a leak in the exhaust stream in between the front and rear O2 sensors, its the same exact principle, it will draw from that leak like a siphon tube so the rear O2 will read lean when the front O2 is reading normal. This confuses the heck out of the ECM and can be seen on the scope when the leak is opened and fresh air enters. http://www.mechadyne-int.com/vva-referen...d-emissions.pdf
 
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Those pulsations still have pressure at the low end, just lower than peak. Add this to having multiple cylinders, and the pressure is always higher than ambient. They are very rapid and average out with a net '+' pressure in the manifold and pipes.
 
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Why not?
Quote:
The fluid can be either a liquid or a gas
Quote:
average out with a net '+' pressure in the manifold and pipes.
So when you back of the throttle quickly you are saying this is still true? It isnt.
 
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