Bolo

My never ending Saga to pass the California smog emmission test...

Finally found and patched (2) vaccum leaks on my car...But my A4 still occasionally Throws a p0171 (System Lean code) ...Even if my failed smog readout is only failing on the CO level... car Running too Rich....Huh??

Mechanic suggest a new (Front) 02 sensor...So I went and order the Bosch (exact fit) model at Rockauto. Initial test drive...car was running like a champ...felt more peppy and boosting great!!..10 mins. on the test drive, check engine light (*GAHH!!!*)...1 new code (P0130)...I notice idle is slightly stumbling.

Code supposed to suggest 02 sensor malfunction...when I erase It... it comes right back after 5 mins. driving. Did I get the wrong Sensor??
More Information for BOSCH 17090
... or did I bought a defective one? Its not OEM...but RockAuto is suggesting it as an exact fit/replacement....

lyleswk

If it were me, I would get an OEM and see if that solves it. "replacements" are sometimes not at the correct depth and will read 02 valves different than the ECU is expecting.

Bolo

Just an Update:.... I went ahead and removed the new 02 Sensor , and re-installed the old Sensor back..
I cleared the Error (p0130) code and drove the car to work and back...Result: No check engine light (no error code all day).
But with the old 02 Sensor back on, the car felt a little less peppy again and asthmatic when boosting.... and time will tell if the old error lean (p0171) code will show up again later on.....

Although the (new) the 02 Sensor definitely improved the cars performance...it plagued the car with p0130 (sensor malfunction) code..& stumbling idle. Is their a way to diagnose a Sensor Plug if its defective/?...most car part sites recommend this Bosch model as a direct replacement for my A4......

lyleswk

When you say most sites, are you referring to some of the better known ones like ECStuning? What does th dealer say?

Good news is you found the issue...

Prospeeder

Your missing the bigger picture with what the code means. It doesnt just mean that the sensor is bad. It means it saw less than .4 volts from the sensor for too long. The sensor is just going to create a voltage signal from oxygen difference on each side of the sensor. So lots of oxygen on both sides (Lean condition) no voltage. Lots of oxygen on outside, none on the other (rich condition) more voltage. So what you have going is a lean condition on that bank causing the oxygen sensor to never change reading because its so lean thus setting the fault p0130.


So with that info. Your bank 1 is lean. You have a air/vacuum leak on that side of the engine most likely. Large exhaust leak from the manifold before the sensor could do this too. I doubt anything is wrong with your sensor its just reporting what its seeing. Good luck.

lyleswk

Good point, but don't you mean the p171 code he originally had versus the p130 code he got with the replacement sensor which is for a faulty sensor? And obtw, 171 troubleshooting doesn't point you to an o2 sensor to begin with.

16555/P0171/000369 - Ross-Tech Wiki

I need to read this stuff more carefully. That's 2 in one week I have missed details on

Bolo

Thats whats confusing me....Putting the Old Sensor back doesn't give me any P0130 (Low voltage code anymore)... ..car will run stable and idle smooth..... But might possibly give me a P0171 (lean code on the long run)..non so far after almost after 100 miles installing old Sensor back..

But The New Sensor Definitely Gives a car more Throttle response and Pep... But will give the car a slight stumbling idle and throw the p0130 code after about 5 mins. driving....

And with both hinting that the car is running lean....The failed Smog Test has a readout stating the CO levels to high...suggesting the car is running too Rich.......confused...

So instead of assuming I bought a defective (New) 02 Sensor...Is the Old Sensor just too worn out to detect the P0130 code which the New one did???

lyleswk

To your very last comment, the O2 sensor doesn't detect voltage, it creates voltage based on the O2 level it "sees". The ECU reads the voltage and based on it's programming, throws codes. My read of the situation is the ECU is detecting a voltage it doesn't "like", i.e. out of expected range, specifcally with the new sensor and therefore dropping the P0130 code. This tells me it is not an appropriate replacement. See link on P0130. Prospeeder input on this

16514/P0130/000304 - Ross-Tech Wiki

Why does it runs better? No idea. You would have to log the car to figure that out and also understand what the ECU does with fuel mixture, timing, etc whne it detects a faulty O2 sensor. But, back to your original problem. As Prospeeder notes, look for obvious leaks. If you follow the link to the troubleshooting for P0171, it has other items to look at. Again, you will note that O2 sensor is not one of the options.

Last thought. If the lean code hasn't come back since you reinstalled the original sensor, maybe leave it alone?

Bolo

Thanks for the Tip....I feel like I'm Getting Close to Getting my A4 finally Pass the dreaded CA smogtest....I really like to achieve this DIY before spending big and surrendering to the dealership or specialize mechanic.

Frustrating cause my old faithfull A4 is still running well...except for the high CO reading which failed it twice already (1.45% vs. 1% Max allowable)....otherwise...not bad for a 12 year old ride with 218K on the odometer.......