JohnAMG

3 weeks my car, 2009 C4S, go CEL and codes I got the P2A01 and P2196. O2 Sensor Circuit Range/Performance Bank 1 Sensor 2 and O2 sensor signal stuck rich Bank 1 sensor 1. The car drove fine so I cleared the code with OBDII scanner. Last week the same code popped up again. So I took the car in to the dealer today and they performed various test to figure out the problem. Later I was told the sensors weren't defective but was told it is very unusual for all 4 sensors to act up. The dealer suspected the Sharkwerk bypass pipes could be the culprit. I told the tech. I had the bypass pipes installed since last summer and never had an issue with it. The tech suggest to get rid of the bypass pipes and reinstall the primary muffler.

Does anyone has exprience with this? Can decrease in back pressure or defective muffler gasket cause this problem? Any suggestion will be greatly appreciated. The only good news from this dealer visit is I got my first oil change for $159.00.

John

canuckporsche

I have the same car with the sharkerks bypass and fabspeed intake. My oxygen sensors went at 5k and the blame at first was on the custom work but in the end it was defective sensors.

Macster

You sure the error code numbers correct? P2XXX is not a power train error number. P2XXX is a chassis error code classification IIRC. (My references are at work and I'm a home.)

Any leak of air into the exhaust system can certainly affect the operation of the O2 sensors and converters.

The engine controller uses a sophisticate algorithm for checking proper operation of the O2 sensors and from this know the converters are working properly. All automakers are responsible for proper engine operation to ensure exhaust emissions do not exceed mandated thresholds.

The EPA constantly checks new and used cars to ensure compliance.

The engine controller can't know a misreading O2 sensor's cause, only that it is not delivering the right numbers and the engine controller's fueling falls within the realm allowed by its static fuel maps.

In some cases an error detected on one side will cause the error codes for both sides to be logged. Thus it is possible for an exhaust air leak on one side of the engine, the exhaust system of one bank, to cause not only errors on that side to be logged but error codes for the other side to be logged as well.

Since the exhaust system is not stock you must ensure the exhaust system changes have not resulted in an exhaust system air leak.

Once you have eliminated this as the cause then bad O2 sensors or mal-functioning converters (due to the changes in the exhaust gas flow, or exhaust gas temperatures produced by the aftermarket exhaust system) or possibly just due to bad converters or bad sensors becomes a possibility.

The dealer understandably so is reluctant to replace the O2 senors when the cause of the problem possibly the aftermarket exhaust system.

By re-installing the factory exhaust system this eliminates the possibility the aftermarket system at the root of the problem. Of course the factory system must be properly re-installed to ensure no exhaust air leaks exist.

Sincerely,

Macster.

JohnAMG

Thank you for the thorough explaination. I put back the OEM primary resonator but the problem persist. It is still P2A01(bank 1 sensor 2) but sometime reads 2196( stuck rich) and 2197( stuck lean). Also at times the car would stutter under accleration. Can poor fuel quaity cause any of these issue? Also are the bank#1 sensors on the driver side? Thanks again.

John

Macster

Poor fuel quality is a pretty expansive label, but sure, well, that is I susppose bad gas could account for the symptoms you report.

But why do you suspect poor fuel quality? Where or with what did you fill the tank?

Be careful with that rich and lean nomenclature. O2 sensors compare the amount of oxygen in the exhaust gas stream to that of outside (atmosphere) air.

If the 02 sensor supplies a reading that indicates there is too much oxygen in the exhaust gases then too little oxygen this suggests the converter is unable to store oxygen for processing exhaust gases. The engine controller constantly varies the engine's fuel/air mixture from slightly (very slightly) rich to very slightly lean. It notes it is able to do this, it has control of the engine's fueling by monitoring the readings from the #1 sensors, those ahead of the converters.

The converters during the lean times retain some excess oxygen -- all the oxygen is not consumed during combustion because there is not enough gasoine to combine with and burn the oxygen -- to use when the exhaust gas stream has less oxgyen. This happens when the engine controller supplies a richer air/fuel mixture to the engine. (You can see this going on by viewing the #1 O2 sensor voltage levels or watching the short term fuel trims.)

Assuming the O2 sensor operating properly this suggests the converter is not functioning properly. It is cold, or is getting outside air, or has worn out, or has had its active metals compromised by contaminates.

One "test" is to switch O2 sensors from side to side. Move the #2 O2 sensor from the right side to left side and the sensor from the right side to the left side.

If you were getting just one error code before on just one side, if the error code follows the sensor the sensor is bad. if the error code stays on the original "bad" side, then something else is going wrong. The converter, or perhaps the O2 sensor connector or even the engine controller is defective. However the sensor's behavior does not indicate the connector is bad or the engine controller is bad.

O2 sensors are rather delicate devices. You do not want to touch their tips and you want to use no thread lube -- new sensors should come with some suitable thread lube already applied to the threads. Use no thread lube with any silicon. There are thread lubes suitable for use with O2 sensors.

Do not attempt to measure the sensor's resistence. This can damage its very delicate and sensitive tip.

If you know what you are doing you can measure the continunity of its heater circuit to ensure the heater portion's working properly. An intermittently failing heater can cause the sensor to react strangely, but generally if "cold" it will just read around 0.45volts which is kind of a no man's land in an O2 sensor's output voltage range of approx 0.1 volts to 0.7 volts.

When I trouble shoot O2 sensors I like to be able to view both the sensor voltages of the #2 sensors or the #1 sensors and also view the short term and long term fuel trims to see what the engine controller is trying to do.

It helps greatly though that at least one side is working normally, cause you have the normal side's readings to compare to the problem side's readings and from then difference generally deduce what's going on, though it can take time cause the bad sensor may only go bad, act up, after some length of operation, then upon engine shut down and immediate restart be just fine, or fine enough to not appear too far from normal.

See if the error code follows the sensor.

Also, if you have reason to suspect bad gas you might consider addressing that. One rather drastic step is by draining the gas tank (be very careful cause of course gas is highly flammable). You might need to if the gas particularly bad use some kind of gas treatment to help neutralize the bad gas in the fuel lines. The fuel filter might need replacing too. Depends upon how bad the gas is and why it was bad. In severe cases of bad gasoline -- or fillling the gas tank with the wrong gas (E85) or diesel fuel the fuel system may need flushing.

Oh, bank one vs. bank 2. Well, I don't know. That is my Boxster's bank one is the passenger side bank (USA car) and bank 2 is the driver's side. So far I've never had to figure out the bank numbering of my Turbo's engine. Anyhow, with the 911 and its unconventional engine positionig..., let me consult my Bosch reference book -- Monday cause it is at work and I'm at home now -- regarding #1 cylinder determination for engines and see if I can answer that.

Or you can disconect a sensor and upon getting check engine light and reading the diagostic trouble code see which error code and bank number assigned to the error code in the description and from that determine the bank numbering.

Sincerely,

Macster.

JohnAMG

Thank you Macster for your response. I got back from dealer and was told the O2 sensor in the left side, before catalytic converter maybe at fault. They ordered the sensor already. However the service advisor don't think there will be a issue with the warranty since I got the OEM primary resonator back on but he needs to verify with the regional rep. Just in cause the dealer decided to screw me, how difficult is to replace the O2 sensor myself? I took the wheel off and got a good look at the O2 sensor today. And it looks to be a fairly simple process and "plug & play" installation. I think the hard part would to loosen up the sensor off the converter, and I presummed I would just have to unscrew the senor off the converter. Any suggestion will be greatly appreciated.

John

Macster

O2 sensor change not hard. The factory manual recommends using a hydraulic fitting wrench or a flare nut wrench. See here:

http://buy1.snapon.com/catalog/item....e=&dir=catalog

The O2 sensor is not made of soft brass but of tougher steel, but I picked up IIRC a Snap On flare nut wrench, but any name brand flare nut wrench should suffice. If you just just the standard open ended wrench pay attention to the flats when you go to loosen the old sensor. If the thing is too tight the flats might start to deform and then you want to get the right wrench.

For me the hardest part was reaching up and undoing the connector clip that held the O2 sensor connector in the wiring harness connector. I've got baby soft hands and not nearly the hand and finger strength I used to have when I worked on cars a lot ( as a hobby ).

Handle the old -- in case it proves to not be the problem -- and new sensor with care. Do not touch the tip. Do not static discharge any electricity into the device. Do not contaminate the sensor tip with anything and do not use any thread lube with silicon. If the sensor comes with dry threads -- and the ones I bought (Bosch) came with some thread lube already applied -- pick up a tube of thread lube for O2 sensors.

Be sure you get the connector snapped home. It may take some force but be sure the pins do not jam or bend.

Route the sensor wiring like the old sensor wiring. If the wiring is left loose it will vibrate and crack after a while or chafe and short out.

Mind you don't overtighten the sensor but it wants to be tight, properly so.

You can buy a crows-foot wrench for use on your torque wrench if you want to go that far.

See here:

http://buy1.snapon.com/catalog/tools...e=snapon-store

Sincerely,

Macster.

madporsche

JohnAMG, did you fix the problem? I was wondering if the O2 sensor was bad since I got the error code, P2196, yesterday.

JohnAMG

It was a bad sensor on the left bank and it was repaired last spring.

John

madporsche

I see. Was it covered by your factory warranty?
By the way, thank you for your help.

JohnAMG

It was covered under warranty. But the dealer made took off my Sharkwerk bypass pipes to make sure the bypass pipes was not causing the faulty reading.

John

Kelv

Hi Macster,
Are 2009 year 997.2 on narrowband oxygen sensors?
You mentioned "...but generally if "cold" it will just read around 0.45volts which is kind of a no man's land in an O2 sensor's output voltage range of approx 0.1 volts to 0.7 volts....".

My understanding is that they are on wideband Oxygen Sensors.
Could you kindly advise, as I'm studying this at the moment, and my mech's info is alittle different.

Thanks again for your advise.