p0136 - Rear o2 Sensor - 99 C230K Troubleshooting
02-09-2010, 12:27 AM
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p0136 - Rear o2 Sensor - 99 C230K Troubleshooting
I do NOT have a CEL light but recently plugged in my very basic OBD II scanner (no live data graphing or anything) and recieved a P0136 code. This the o2 Sensor Circuit Malfunction (Bank 1, Sensor 2) error which indicates the o2 oxygen sensor after the catalytic converter. There are no other codes.
When I try to clear the code with my scanner, the code comes back immediately without even starting the engine.
My 99 c230 Kompressor with the M111.975 engine has just under 40k miles. The gas mileage has been low for quite some time but the car runs smoothly and doesn’t misfire. I recently replaced the MAF with a new Bosch unit from Autohausaz.com but the code was there before the MAF replacement and after (it is a long story but I have had a suspicion my MAF was unreliable for a long time). I am very confident that all of the intake connections from the intercooler back to the throttle body (including the MAF) are not leaking.
Any help troubleshooting this would be appreciated. Is this one of those issues where I need to go get it diagnosed with a high tech system like the Mercedes SDS diagnostics versus just replacing o2 sensor or is it pretty certain with this code that the problem is going to be sensor itself?
Is it possible on the w202 C Class to disconnect the rubber exhaust hangers from the cat back and be able to get enough clearance to swap out the rear o2 sensor (unfortunately located on the top side of the exhaust piping!) with the car up on ramps or do I have to disassemble the whole exhaust system?
Is an o2 socket wrench necessary or will an open wrench work just fine? If a socket is necessary, is the full socket (like a lawn mower spark plug wrench) best or is the smaller crow’s foot type better?
Any advice would be appreciated.
Thanks!
When I try to clear the code with my scanner, the code comes back immediately without even starting the engine.
My 99 c230 Kompressor with the M111.975 engine has just under 40k miles. The gas mileage has been low for quite some time but the car runs smoothly and doesn’t misfire. I recently replaced the MAF with a new Bosch unit from Autohausaz.com but the code was there before the MAF replacement and after (it is a long story but I have had a suspicion my MAF was unreliable for a long time). I am very confident that all of the intake connections from the intercooler back to the throttle body (including the MAF) are not leaking.
Any help troubleshooting this would be appreciated. Is this one of those issues where I need to go get it diagnosed with a high tech system like the Mercedes SDS diagnostics versus just replacing o2 sensor or is it pretty certain with this code that the problem is going to be sensor itself?
Is it possible on the w202 C Class to disconnect the rubber exhaust hangers from the cat back and be able to get enough clearance to swap out the rear o2 sensor (unfortunately located on the top side of the exhaust piping!) with the car up on ramps or do I have to disassemble the whole exhaust system?
Is an o2 socket wrench necessary or will an open wrench work just fine? If a socket is necessary, is the full socket (like a lawn mower spark plug wrench) best or is the smaller crow’s foot type better?
Any advice would be appreciated.
Thanks!
Last edited by xvvvz; 02-09-2010 at 12:31 AM.
11-22-2013, 02:19 PM
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'99 C230
I know this post is old..but i am having a similar issue, hopefully bringing this back to light will give way to someone responding with a solution since i can't find one anywhere online.
I am getting a p0170 code and i know it's not the MAF. I've cleaned it and don't think it needs replacing. I got the front o2 sensor off, which needs a 3/8 o2 sensor socket(i advise getting it, just a few bucks)
Instead of replacing the sensor with a new one i actually cleaned it with a blowtorch and when i put it back on i saw an increase in performance. However, this was one of two or however many o2 sensors there are.
So i am lead to believe the back o2 sensor needs to be cleaned or replaced, but i can't find it. If it is above the exhaust then my question is the same as Xvvvz. What's the shortest way to get that o2 sensor off? Any ideas?
I am getting a p0170 code and i know it's not the MAF. I've cleaned it and don't think it needs replacing. I got the front o2 sensor off, which needs a 3/8 o2 sensor socket(i advise getting it, just a few bucks)
Instead of replacing the sensor with a new one i actually cleaned it with a blowtorch and when i put it back on i saw an increase in performance. However, this was one of two or however many o2 sensors there are.
So i am lead to believe the back o2 sensor needs to be cleaned or replaced, but i can't find it. If it is above the exhaust then my question is the same as Xvvvz. What's the shortest way to get that o2 sensor off? Any ideas?
