2006 997 Oxygen Sensor or Cat?
11-15-2016, 04:58 PM
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2006 997 Oxygen Sensor or Cat?
I have a 2006 997 Stock except for AP Mufflers. Cats are stock car has 60k miles. I'm getting a code P0420 Bank one Sensor 2. My Mechanic said its probably the Cat but we didn't get into heavy diagnostics. I have a code scanner when I monitor the voltage on both post 02 sensors the readings are comparable between the two normal fluctuation. On Idle the O2 sensor in Bank one is all over the place. 0.140V to .0750v on Idle. The O2 sensor on Bank two stays around .0750v Would the fluctuation on the Bank one sensor indicate a bad sensor since its around 0.140V or does this lean more towards an issue with the CAT? Any help would be greatly appreciated. Thank you,
11-16-2016, 07:27 AM
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I have a 2006 997 Stock except for AP Mufflers. Cats are stock car has 60k miles. I'm getting a code P0420 Bank one Sensor 2. My Mechanic said its probably the Cat but we didn't get into heavy diagnostics. I have a code scanner when I monitor the voltage on both post 02 sensors the readings are comparable between the two normal fluctuation. On Idle the O2 sensor in Bank one is all over the place. 0.140V to .0750v on Idle. The O2 sensor on Bank two stays around .0750v Would the fluctuation on the Bank one sensor indicate a bad sensor since its around 0.140V or does this lean more towards an issue with the CAT? Any help would be greatly appreciated. Thank you,
It does not help to suggest that it it is probably the cat as the cats rarely fail (they do sometimes).
Easiest and cheaper is to swap your O2 sensor with the other bank. If the same code shows up, your cat might be toast. Check for exhaust and vacuum leaks first. Most likely it is just a bad O2 sensor...
11-16-2016, 10:03 AM
#6
Nordschleife Master
This is what you do : my answer from his other thread.
https://rennlist.com/forums/997-foru...tml?styleid=13
https://rennlist.com/forums/997-foru...tml?styleid=13
In most cases it's the cat. But I never swap parts without testing.
First :
Make sure you're in closed loop. Secondly,a downstream O2 sensor should not fluctuate up and down around stoichiometric when the cat is hot. It should look linear on a graph. If it's fluctuating the same as the upstream from the same bank,you have a bad cat.
By disconnecting the sensor and reading around 0.5V on the scan tool it tells you circuit integrity and computer are fine. That is what's called a " bias voltage "...the computer is sending that voltage for testing. If you didn't have a bias voltage system,you would disconnect the sensor and look on the harness side for the signal wire. In most Bosch sensors you have 2 white wires for the heater,a grey and a black for signal. You would T-pin the signal wire and use a test light from battery positive to drive that signal high while looking at the scan tool. You can even use your body to drive that signal high : one hand to battery positive and one hand on the T-pin. But you don't have to do all that,your system is fine because you see bias voltage at the computer.
A good O2 sensor can oscillate between 0 and 1V,which is exactly what seems that yours is doing.
VERY IMPORTANT : Before calling a bad cat,MAKE SURE you DO NOT have any exhaust leaks before the cat!!!!!!! I can't stress this enough!
Lastly : cats don't usually fail easily UNLESS there's a problem with how the engine is running. Make sure it's running properly.
One more point : in the US by law,manufacturers cover cats for up to 8 years(or 10...can't remember) or 80K miles. Might want to check into that...
First :
Make sure you're in closed loop. Secondly,a downstream O2 sensor should not fluctuate up and down around stoichiometric when the cat is hot. It should look linear on a graph. If it's fluctuating the same as the upstream from the same bank,you have a bad cat.
By disconnecting the sensor and reading around 0.5V on the scan tool it tells you circuit integrity and computer are fine. That is what's called a " bias voltage "...the computer is sending that voltage for testing. If you didn't have a bias voltage system,you would disconnect the sensor and look on the harness side for the signal wire. In most Bosch sensors you have 2 white wires for the heater,a grey and a black for signal. You would T-pin the signal wire and use a test light from battery positive to drive that signal high while looking at the scan tool. You can even use your body to drive that signal high : one hand to battery positive and one hand on the T-pin. But you don't have to do all that,your system is fine because you see bias voltage at the computer.
A good O2 sensor can oscillate between 0 and 1V,which is exactly what seems that yours is doing.
VERY IMPORTANT : Before calling a bad cat,MAKE SURE you DO NOT have any exhaust leaks before the cat!!!!!!! I can't stress this enough!
Lastly : cats don't usually fail easily UNLESS there's a problem with how the engine is running. Make sure it's running properly.
One more point : in the US by law,manufacturers cover cats for up to 8 years(or 10...can't remember) or 80K miles. Might want to check into that...
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11-16-2016, 11:17 AM
#8
10 years or so is about the lifespan of an 02 sensor. That degrade over time too, affecting power output and mileage. They are made of soft metal, and good luck getting them off without mangling it if its been own there 10 years. Some cars the cats with sensors and not exposed to elements, on the 997 its right under the car and prone to getting rusted/crusted on. I was going to mod my 07 with high flow cats and the tech tole me that more than likely when taking the sensors off they would get mangled up from being corroded on. So all I'm saying is that sure, try the swap but if you don't have any new ones around....then you have to go get them anyhow.
11-16-2016, 12:09 PM
#9
Race Director
I have a 2006 997 Stock except for AP Mufflers. Cats are stock car has 60k miles. I'm getting a code P0420 Bank one Sensor 2. My Mechanic said its probably the Cat but we didn't get into heavy diagnostics. I have a code scanner when I monitor the voltage on both post 02 sensors the readings are comparable between the two normal fluctuation. On Idle the O2 sensor in Bank one is all over the place. 0.140V to .0750v on Idle. The O2 sensor on Bank two stays around .0750v Would the fluctuation on the Bank one sensor indicate a bad sensor since its around 0.140V or does this lean more towards an issue with the CAT? Any help would be greatly appreciated. Thank you,
Normally the Bank 1 and Bank 2 #2 sensor voltages will be in the 0.6V to 0.7V range. This indicates a lack of oxygen in the exhaust that leaves the converters which is a sign the converter is working properly, it is using stored oxygen to process the exhaust gases.
The behavior of the Bank 1 #1 sensor is normal. The DME varies the air/fuel mixture just a bit on either side of ideal. It does this and monitors the #1 sensor voltage level to know it has control of the fueling.
Additionally this swing from a bit too rich to a bit too lean provides extra oxygen to the converters which store this oxygen to use for their operation.
If the Bank 2 #1 sensor voltage remains at 0.75V that's a sign the sensor is bad.
The factory workshop manual says -- in so many words -- that in the event of a P0420/P0430 error if there are any O2 sensor aging or other sensor related error codes to replace the indicated sensors then clear the codes and road test the car. If the P0420/P0430 error codes come back to replace the indicated converters.
I have to repeat myself: You must be sure of the sensor positions and the readings. It is normal for the #1 sensor of both banks to swing from 0.1V to 0.7V.
If you observe a #1 sensor with a reading that is flatlined at any voltage that is probably a sign the sensor is bad.
If you observe a #2 sensor with a reading that is low, way down in the 0.1V range (though really much below 0.6V) that's a probably a sign the sensor is bad.
If you find a bad sensor my recommendation is to replace all 4 sensors. They have all covered the same miles. While the others still work their response times are slowing and their performance then less than optimium. The result is the DME can fuel the engine less accurately because of this.
I recall when my 2003 Turbo starting manifesting an O2 sensor error (at around 132K miles) I had all 4 sensors replaced. The engine ran noticably better afterwards and yet it felt before hand it was running the same as always.
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quino987 (01-29-2020)
11-11-2021, 10:18 AM
#10
You have to be sure of your sensor locations. #1 sensors are located *before* the converters. #2 sensors are located *after* the converters.
Normally the Bank 1 and Bank 2 #2 sensor voltages will be in the 0.6V to 0.7V range. This indicates a lack of oxygen in the exhaust that leaves the converters which is a sign the converter is working properly, it is using stored oxygen to process the exhaust gases.
The behavior of the Bank 1 #1 sensor is normal. The DME varies the air/fuel mixture just a bit on either side of ideal. It does this and monitors the #1 sensor voltage level to know it has control of the fueling.
Additionally this swing from a bit too rich to a bit too lean provides extra oxygen to the converters which store this oxygen to use for their operation.
If the Bank 2 #1 sensor voltage remains at 0.75V that's a sign the sensor is bad.
The factory workshop manual says -- in so many words -- that in the event of a P0420/P0430 error if there are any O2 sensor aging or other sensor related error codes to replace the indicated sensors then clear the codes and road test the car. If the P0420/P0430 error codes come back to replace the indicated converters.
I have to repeat myself: You must be sure of the sensor positions and the readings. It is normal for the #1 sensor of both banks to swing from 0.1V to 0.7V.
If you observe a #1 sensor with a reading that is flatlined at any voltage that is probably a sign the sensor is bad.
If you observe a #2 sensor with a reading that is low, way down in the 0.1V range (though really much below 0.6V) that's a probably a sign the sensor is bad.
If you find a bad sensor my recommendation is to replace all 4 sensors. They have all covered the same miles. While the others still work their response times are slowing and their performance then less than optimium. The result is the DME can fuel the engine less accurately because of this.
I recall when my 2003 Turbo starting manifesting an O2 sensor error (at around 132K miles) I had all 4 sensors replaced. The engine ran noticably better afterwards and yet it felt before hand it was running the same as always.
Normally the Bank 1 and Bank 2 #2 sensor voltages will be in the 0.6V to 0.7V range. This indicates a lack of oxygen in the exhaust that leaves the converters which is a sign the converter is working properly, it is using stored oxygen to process the exhaust gases.
The behavior of the Bank 1 #1 sensor is normal. The DME varies the air/fuel mixture just a bit on either side of ideal. It does this and monitors the #1 sensor voltage level to know it has control of the fueling.
Additionally this swing from a bit too rich to a bit too lean provides extra oxygen to the converters which store this oxygen to use for their operation.
If the Bank 2 #1 sensor voltage remains at 0.75V that's a sign the sensor is bad.
The factory workshop manual says -- in so many words -- that in the event of a P0420/P0430 error if there are any O2 sensor aging or other sensor related error codes to replace the indicated sensors then clear the codes and road test the car. If the P0420/P0430 error codes come back to replace the indicated converters.
I have to repeat myself: You must be sure of the sensor positions and the readings. It is normal for the #1 sensor of both banks to swing from 0.1V to 0.7V.
If you observe a #1 sensor with a reading that is flatlined at any voltage that is probably a sign the sensor is bad.
If you observe a #2 sensor with a reading that is low, way down in the 0.1V range (though really much below 0.6V) that's a probably a sign the sensor is bad.
If you find a bad sensor my recommendation is to replace all 4 sensors. They have all covered the same miles. While the others still work their response times are slowing and their performance then less than optimium. The result is the DME can fuel the engine less accurately because of this.
I recall when my 2003 Turbo starting manifesting an O2 sensor error (at around 132K miles) I had all 4 sensors replaced. The engine ran noticably better afterwards and yet it felt before hand it was running the same as always.
11-28-2021, 02:07 PM
#11
This thread in the end shows similar voltages to what I get on my o2 sensor durametric test. But they didn’t get addressed. Is the -50 volts a sign of the bias voltage from the computer and a sign that the o2 sensor is not reading a voltage. I’m thinking of disconnecting one o2 sensor to test that. Maybe the ECU has a bad connection?