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1999 SLK 230
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34 Posts
Discussion Starter #1
I had the autozone guy look these up, the CEL came on while putting around the city today. I know that the car had an intermittent misfire a month ago and I changed plugs (ok, I had it done) and it has been fine so far. The print out on these codes points to the 02 sensor on bank 1 sensor 1, however I also hear that the 02 sensor is the most replaced part for no reason on most models. So, my question is...how do I verify whether it is an 02 sensor or misfire, the misfire is third option on both codes for causing the fault.

Thanks for any help, I live 170 miles from the nearest MB tech, at least one that I would let touch my car...there is one 80 miles away but they charge way too much and do poor work. So, I need to know what I am looking at when I take it to a local wrench.
 

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Registered
2006 SLK350
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5 Posts
I had the autozone guy look these up, the CEL came on while putting around the city today. I know that the car had an intermittent misfire a month ago and I changed plugs (ok, I had it done) and it has been fine so far. The print out on these codes points to the 02 sensor on bank 1 sensor 1, however I also hear that the 02 sensor is the most replaced part for no reason on most models. So, my question is...how do I verify whether it is an 02 sensor or misfire, the misfire is third option on both codes for causing the fault.

Thanks for any help, I live 170 miles from the nearest MB tech, at least one that I would let touch my car...there is one 80 miles away but they charge way too much and do poor work. So, I need to know what I am looking at when I take it to a local wrench.
Hello,

Seeing your post jogged my memory about my 2001 SLK. I no longer have this car, only because it was destroyed in a fire. I had to replace my oxygen sensor several times while I owned it, until I finally got tired of replacing them every year. I initially attributed their failure to my short trips back and forth to work, as the car barely got warmed up, it concerned me enough that I would take it for a nice cruise down the freeway about once or twice a week. What ultimately ended up being the culprit was a defective cam position actuator. The 01 SLK (and I assume yours as well) has variable valve timing on the intake cam. There is a electro-hydraulic actuator mounted on the front of the engine that changes the cam position as directed by the ECU.

According to the M-B dealer, these actuators have a tendency to develop a leak that forces oil into the wiring harness. I would have never believed that this could cause the failure of the oxygen sensor, or that the oil could travel that far in the harness, although I did notice one time when I was changing the sensor myself there was some oily residue inside the electrical connector for the sensor. The dealer also told me I was fortunate to have the problem corrected when I did, as the oil can also find its way into the ECU and cause problems there. I always thought the oily stuff was there on purpose, kind of like the goop you see in some connectors to prevent corrosion.

Since I no longer have the car, I can't say if the replacement of the actuator fixed the car once and for all, but I did not have to replace any more sensors while I did have it. I don't check this section of the forums too often anymore for the same reason. Anyway, something to consider. Good Luck!
 

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Registered
1999 SLK 230
Joined
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34 Posts
Discussion Starter #3
Hello,

Seeing your post jogged my memory about my 2001 SLK. I no longer have this car, only because it was destroyed in a fire. I had to replace my oxygen sensor several times while I owned it, until I finally got tired of replacing them every year. I initially attributed their failure to my short trips back and forth to work, as the car barely got warmed up, it concerned me enough that I would take it for a nice cruise down the freeway about once or twice a week. What ultimately ended up being the culprit was a defective cam position actuator. The 01 SLK (and I assume yours as well) has variable valve timing on the intake cam. There is a electro-hydraulic actuator mounted on the front of the engine that changes the cam position as directed by the ECU.

According to the M-B dealer, these actuators have a tendency to develop a leak that forces oil into the wiring harness. I would have never believed that this could cause the failure of the oxygen sensor, or that the oil could travel that far in the harness, although I did notice one time when I was changing the sensor myself there was some oily residue inside the electrical connector for the sensor. The dealer also told me I was fortunate to have the problem corrected when I did, as the oil can also find its way into the ECU and cause problems there. I always thought the oily stuff was there on purpose, kind of like the goop you see in some connectors to prevent corrosion.

Since I no longer have the car, I can't say if the replacement of the actuator fixed the car once and for all, but I did not have to replace any more sensors while I did have it. I don't check this section of the forums too often anymore for the same reason. Anyway, something to consider. Good Luck!
Is there any way to check the cam position sensor for an oil leak without having to completely disassemble the front of the motor?
 

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Registered
2006 SLK350
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5 Posts
I can't tell you exactly how to check if the actuator is leaking oil into the harness, I don't have my SLK230 anymore so I could look, but if I remember correctly there is a plastic cover over the front of the engine, and if that were removed, pull off the electrical connector on the actuator, if there is oil inside, you might have a problem. You could also pull the connectors off the ECU, (passenger side, rear of engine compartment, disconnect the battery first). If you find oil there, the actuator is leaking.
 

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Premium Member
1999 SLK230 Sport
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2,713 Posts
I had a P0170 this past weekend. Removed the MAF sensor, used ample amounts of CRC MAF Sensor Cleaner and viola...Code Cleared.
 

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Registered
1999 SLK 230
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34 Posts
Discussion Starter #6
Thanks all for the help, I replaced the O2 sensor and the MAF, figured with 115,000+ miles it couldn't hurt anyway, so teh codes cleared and the car is running great...now if the weather would just be nice.
 
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