P2097 after replacing both post-cat O2 sensors?
08-06-2017, 01:31 AM
#1
Cruisin'
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P2097 after replacing both post-cat O2 sensors?
After buying my 2007 Cayman S in early June, I started getting a CEL which, after pulling the codes, ended up being a P2097 - Post Catalyst Fuel Trim System Too Rich Bank 1. The car has 120k miles, and my initial research pulled up that the post-cat O2 sensors were probably bad. I replaced both sensors just to be safe, and everything was fine for a while. In the last week or two, I've started getting the same CEL/code coming up again and now I'm concerned that it's something else. It doesn't sound like I have an exhaust leak anywhere, which is making me look at the cats possibly going bad. Is there any easy way for me to check that myself? Also, could it still be related to the O2 sensors in any way?
08-06-2017, 02:49 AM
#2
I haddah Google dat
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The O2 sensors that do all the work would be the pre-cat sensors, right?
Edit: come to think of it, I had a similar problem in the Benz. i can't recall the code at the moment. But the fix was to replace the cat.
Edit: come to think of it, I had a similar problem in the Benz. i can't recall the code at the moment. But the fix was to replace the cat.
08-06-2017, 04:12 PM
#3
Race Director
After buying my 2007 Cayman S in early June, I started getting a CEL which, after pulling the codes, ended up being a P2097 - Post Catalyst Fuel Trim System Too Rich Bank 1. The car has 120k miles, and my initial research pulled up that the post-cat O2 sensors were probably bad. I replaced both sensors just to be safe, and everything was fine for a while. In the last week or two, I've started getting the same CEL/code coming up again and now I'm concerned that it's something else. It doesn't sound like I have an exhaust leak anywhere, which is making me look at the cats possibly going bad. Is there any easy way for me to check that myself? Also, could it still be related to the O2 sensors in any way?
Diagnosing a bad converter can be difficult. All you have to go on is the #2 sensor reading. (Unless you have access to a 4-gas exhaust gas analyzer.)
With everything up to temperature the #1 sensors should read from around a low of 0.1 volt (or a bit less) to high of 0.7 volt (or a bit more).
A very low reading is a presence of oxygen in the exhaust gas. A very high reading is an absence of oxygen in the exhaust gas.
A problem with the readings when viewed in real time and using an OBD2 code reader/data viewer/logger is the readings are not spaced that close together. Thus you won't see the lowest or highest voltage readings except every once in while.
(The DME varies the fuel from lean to rich at idle about every second.)
To see the voltage level at all times a scope can be used with a special break out box to capture the actual voltage levels the sensors are producing.
The #2 sensors should read around 0.7 volt.This reading is an absence of oxygen in the exhaust gas and because the DME knows it added extra oxygen (the really low reading from the #1 sensors) the assumption is the converter is working. It is able to store oxygen and the oxygen is being used to convert the exhaust gases.
If the converter is bad the #2 sensor reading will drop. If it stalls at around 0.45 volt this is a sign the sensor is not working. This can be due to a bad heater but the DME should recognize this and log an error. (This is another reason why you need to check for any pending errors.)
However, if there is an exhaust leak after the converter this can account for the flat line 0.45 volt reading.
If the reading goes lower this is a sign the sensor is working but the converter is letting oxygen through and this is a sign the converter is bad, well, mabye not bad, maybe just not working right due to an exhaust leak.
The converter needs to be hot to work and if there is an exhaust leak before the converter this can impact the converter's performance and as a result it will cool down.
Let me add since you are seeing the error code only from one bank this suggests the other bank is fine. You can -- be very very careful handling sensors! -- swap the #2 sensors from side to side to see if the error follows the sensor or stays put. If it stays put this suggests the problem is not the sensor but with the converter though you want to be sure there is no exhaust leak. A converter is very expensive.
08-06-2017, 06:25 PM
#4
Race Director
How about some O2 sensor data?...
Because I was curious and remembered I have here with me another and much newer OBD2 scan tool -- an Auto-Xray -- with more features than my trusty (and rusty...) Actron -- the Actron has been a good unit just that the Auto-Xray's much newer and has more features (and probably cost more too) -- I decided to view O2 sensor voltages over a span of time and record them.
One feature the Auto-Xray offers is the abilty to capture up to 300 readings (approx. 5 minutes worth) vs. the Actron's 60 second data capture limit.
I connected the Auto-Xray to my 2002 Boxster. The O2 sensors were replaced (at the dealer) 8K miles ago.
After some errand running and back home with everyting nice and warm: Engine coolant at 210F and intake air temperature a bit over 100F (it is only around 82F here now but intake air temp always runs 10F or higher than ambient); I used the Auto-Xray to capture nearly 150 O2 voltage samples.
With nearly 150 samples at idle the low and high readings for each sensor are as follows.
Bank #1 #1: 0.079V to 0.760V
Bank #2 #1: 0.094V to 0.746V
Might add a graph (the Auto-Xray has some graphing capability) of the above data showed some pretty symetrical/regular sine waves.
Bank #1 #2: 0.654V to 0.731V.
Bank #2 #2: 0.539V to 0.741V.
Might mention I'm dealing with a P1128 error with my Boxster and when the error is recorded the freeze frame data has both long term fuel trims in the negative -8% to -10% range.
Just this AM I cleeared this code which set (among other things) all the long term fuel trims to their factory defaults: 0%.
Even so when I took the above samples the #1 long term fuel trim was already -4% and the short term fuel trim was -4%. No doubt the DME was well on its way to logging another P1128. (I think the MAF is the source of the P1128.)
Still I think the above voltages give you something to have as a reference of some sorts when you view the O2 sensor voltages of your car.
Also, as I was using the Auto-Xray tool I remembered that the more sophisticated OBD2 code readers/scan tools have the abillty to trigger O2 sensor tests that are supported by the DME. I now recall that in the past with my Boxster having used this feature with my Actron to test the O2 sensors and in at least one case I can recall over the years the test results confirmed my suspicion (based on the error code) the sensor an error code flagged as bad was in fact bad based on the test results. Believe it or not after over 313K miles I've only replaced the O2 sensors 2 times the last time at 305K miles.
(And in over 156K miles with my 996 Turbo I've only replaced the O2 senors once, at 132K miles.)
One feature the Auto-Xray offers is the abilty to capture up to 300 readings (approx. 5 minutes worth) vs. the Actron's 60 second data capture limit.
I connected the Auto-Xray to my 2002 Boxster. The O2 sensors were replaced (at the dealer) 8K miles ago.
After some errand running and back home with everyting nice and warm: Engine coolant at 210F and intake air temperature a bit over 100F (it is only around 82F here now but intake air temp always runs 10F or higher than ambient); I used the Auto-Xray to capture nearly 150 O2 voltage samples.
With nearly 150 samples at idle the low and high readings for each sensor are as follows.
Bank #1 #1: 0.079V to 0.760V
Bank #2 #1: 0.094V to 0.746V
Might add a graph (the Auto-Xray has some graphing capability) of the above data showed some pretty symetrical/regular sine waves.
Bank #1 #2: 0.654V to 0.731V.
Bank #2 #2: 0.539V to 0.741V.
Might mention I'm dealing with a P1128 error with my Boxster and when the error is recorded the freeze frame data has both long term fuel trims in the negative -8% to -10% range.
Just this AM I cleeared this code which set (among other things) all the long term fuel trims to their factory defaults: 0%.
Even so when I took the above samples the #1 long term fuel trim was already -4% and the short term fuel trim was -4%. No doubt the DME was well on its way to logging another P1128. (I think the MAF is the source of the P1128.)
Still I think the above voltages give you something to have as a reference of some sorts when you view the O2 sensor voltages of your car.
Also, as I was using the Auto-Xray tool I remembered that the more sophisticated OBD2 code readers/scan tools have the abillty to trigger O2 sensor tests that are supported by the DME. I now recall that in the past with my Boxster having used this feature with my Actron to test the O2 sensors and in at least one case I can recall over the years the test results confirmed my suspicion (based on the error code) the sensor an error code flagged as bad was in fact bad based on the test results. Believe it or not after over 313K miles I've only replaced the O2 sensors 2 times the last time at 305K miles.
(And in over 156K miles with my 996 Turbo I've only replaced the O2 senors once, at 132K miles.)
08-06-2017, 07:13 PM
#5
Cruisin'
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Because I was curious and remembered I have here with me another and much newer OBD2 scan tool -- an Auto-Xray -- with more features than my trusty (and rusty...) Actron -- the Actron has been a good unit just that the Auto-Xray's much newer and has more features (and probably cost more too) -- I decided to view O2 sensor voltages over a span of time and record them.
One feature the Auto-Xray offers is the abilty to capture up to 300 readings (approx. 5 minutes worth) vs. the Actron's 60 second data capture limit.
I connected the Auto-Xray to my 2002 Boxster. The O2 sensors were replaced (at the dealer) 8K miles ago.
After some errand running and back home with everyting nice and warm: Engine coolant at 210F and intake air temperature a bit over 100F (it is only around 82F here now but intake air temp always runs 10F or higher than ambient); I used the Auto-Xray to capture nearly 150 O2 voltage samples.
With nearly 150 samples at idle the low and high readings for each sensor are as follows.
Bank #1 #1: 0.079V to 0.760V
Bank #2 #1: 0.094V to 0.746V
Might add a graph (the Auto-Xray has some graphing capability) of the above data showed some pretty symetrical/regular sine waves.
Bank #1 #2: 0.654V to 0.731V.
Bank #2 #2: 0.539V to 0.741V.
Might mention I'm dealing with a P1128 error with my Boxster and when the error is recorded the freeze frame data has both long term fuel trims in the negative -8% to -10% range.
Just this AM I cleeared this code which set (among other things) all the long term fuel trims to their factory defaults: 0%.
Even so when I took the above samples the #1 long term fuel trim was already -4% and the short term fuel trim was -4%. No doubt the DME was well on its way to logging another P1128. (I think the MAF is the source of the P1128.)
Still I think the above voltages give you something to have as a reference of some sorts when you view the O2 sensor voltages of your car.
Also, as I was using the Auto-Xray tool I remembered that the more sophisticated OBD2 code readers/scan tools have the abillty to trigger O2 sensor tests that are supported by the DME. I now recall that in the past with my Boxster having used this feature with my Actron to test the O2 sensors and in at least one case I can recall over the years the test results confirmed my suspicion (based on the error code) the sensor an error code flagged as bad was in fact bad based on the test results. Believe it or not after over 313K miles I've only replaced the O2 sensors 2 times the last time at 305K miles.
(And in over 156K miles with my 996 Turbo I've only replaced the O2 senors once, at 132K miles.)
One feature the Auto-Xray offers is the abilty to capture up to 300 readings (approx. 5 minutes worth) vs. the Actron's 60 second data capture limit.
I connected the Auto-Xray to my 2002 Boxster. The O2 sensors were replaced (at the dealer) 8K miles ago.
After some errand running and back home with everyting nice and warm: Engine coolant at 210F and intake air temperature a bit over 100F (it is only around 82F here now but intake air temp always runs 10F or higher than ambient); I used the Auto-Xray to capture nearly 150 O2 voltage samples.
With nearly 150 samples at idle the low and high readings for each sensor are as follows.
Bank #1 #1: 0.079V to 0.760V
Bank #2 #1: 0.094V to 0.746V
Might add a graph (the Auto-Xray has some graphing capability) of the above data showed some pretty symetrical/regular sine waves.
Bank #1 #2: 0.654V to 0.731V.
Bank #2 #2: 0.539V to 0.741V.
Might mention I'm dealing with a P1128 error with my Boxster and when the error is recorded the freeze frame data has both long term fuel trims in the negative -8% to -10% range.
Just this AM I cleeared this code which set (among other things) all the long term fuel trims to their factory defaults: 0%.
Even so when I took the above samples the #1 long term fuel trim was already -4% and the short term fuel trim was -4%. No doubt the DME was well on its way to logging another P1128. (I think the MAF is the source of the P1128.)
Still I think the above voltages give you something to have as a reference of some sorts when you view the O2 sensor voltages of your car.
Also, as I was using the Auto-Xray tool I remembered that the more sophisticated OBD2 code readers/scan tools have the abillty to trigger O2 sensor tests that are supported by the DME. I now recall that in the past with my Boxster having used this feature with my Actron to test the O2 sensors and in at least one case I can recall over the years the test results confirmed my suspicion (based on the error code) the sensor an error code flagged as bad was in fact bad based on the test results. Believe it or not after over 313K miles I've only replaced the O2 sensors 2 times the last time at 305K miles.
(And in over 156K miles with my 996 Turbo I've only replaced the O2 senors once, at 132K miles.)
08-07-2017, 02:39 AM
#6
I haddah Google dat
Rennlist Member
Rennlist Member
I've graphed the O2 sensor voltages with my Bosch enhanced OBD II scanner. I've not tried it with the Durametric, but probably much better with that. If the curve looks lazy, then chances could be the sensors are in need of replacement. If not, then they're working and could be the cats.
Here's Pt 1 of a basic video explaining fuel trim:
Here's Pt 1 of a basic video explaining fuel trim:
08-09-2017, 05:06 PM
#7
Instructor
I would not discount air leaks from the exhaust gaskets, manifold or even on the plenum/throttle body and would get all exhaust gaskets replaced and a smoke test run on the intake side. Tiny leaks making little external noise are difficult to detect.
Another useful test would be to use an exhaust analyser to determine whether the emitted exhaust gasses are within specification.
Another useful test would be to use an exhaust analyser to determine whether the emitted exhaust gasses are within specification.