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1991 500SL
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Discussion Starter #1
The check engine light came on, on my 91 500SL, and i checked the code with the self diagnostic pushbutton and it gave me code 17. Code 17 is according to the CS1000
Fault Code Scanner pdf "Oxygen sensor signal wire shorted to positive or ground". I installed a new OEM Oxygen sensor and reset the code. The CEL went away for a day or two but came back again. Again with code 17. Any ideas what the problem could be?
 

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1991 500SL
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26 Posts
Discussion Starter #2
Any ideas anyone? I also have a rough idle especially when the car is cold, any connection to the code 17
 

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1992 500SL
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4 Posts
I have the exact same problem

'92 500sl. Code 17, with rough idle and stumble accelerating off idle. I replaced the O2 sensor and was good for 2 days and then check engine light came back on and same code 17, although the car is still running much better since I replaced the sensor.

Did you ever figure out what the problem was with your car?
 

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Greek God of the R129
SL500-500SEL-190E
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8,541 Posts
If you have 02 sensor wires short to ground, like touching the drive shaft.
It may damage the module up stream.
Can't remember module location and part number.

Regards,
aam.
 

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1992 500SL
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4 Posts
No visible short on O2 wires under car

Thanks for the quick reply. When I changed the O2 sensor last weekend the old one was still properly installed, with the two plastic cable clips holding the sensor wires away from the driveshaft. I installed the new one using the same clips. I did notice that the three pin connector felt a little loose to me in the socket even after the plastic locking ring was turned into the locked position. I was wondering if this was normal or if possibly I did not get the connector seated properly. I'm going to get under there again this saturday and double check that. I was thinking that if it had come loose the rough running would have returned with the check engine light, but the car is still running well. Prior to changing the sensor it stumbled hard off of idle and even from a slow speed if I snapped open the throttle too quickly.
 

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I have the exact same problem on my Dad's car. Code 17, found bad O2, replaced O2, ran better but light and code back in a couple days but running better still.

Thoughts?

Thanks
 

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1992 500SL
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4 Posts
I still have not figured this out and it is driving me nuts. Can is running great otherwise. Anyone have any ideas other than wires grounded to driveshaft (which is definitely not the case with mine.) Fuse on overload relay is good also. I have not replaced the relay itself. Anyone know what the part number is for the module which reads the O2 signal?
 

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1990 R129
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75 Posts
I will join the Code 17 club.
My 1990 500SL is doing this as well. Severe bogging down after quarter throttle. Sometimes, something "clicks in" and it runs normally.
I wish I knew where the wires go (I know they are under the passenger footwell.)
Does it lead to the MAS, or Overload, or the main ECU??
 

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Outstanding Contributor
2003 SL500, 2003 SL55, 1998 SL500, (2) 1991 300SLs
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4,536 Posts
Severe bogging down after quarter throttle.
I don't think code 17 has anything to do with this.

The consequence of code 17 is that your fuel mixture control is "open loop", and the engine controller is not tweaking the mixture in accord with the signal from the oxygen sensor.

I wish I knew where the wires go...
I don't know which wires you refer to.
 

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1990 R129
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75 Posts
I don't think code 17 has anything to do with this.

The consequence of code 17 is that your fuel mixture control is "open loop", and the engine controller is not tweaking the mixture in accord with the signal from the oxygen sensor.

I don't know which wires you refer to.
I mean, I don't know where to test continuity of the wires from the oxygen sensor, to...where?

I suppose I could replace the O2 sensor AGAIN...
 

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1992 500SL 129.066
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124 Posts
Hello,

I have the same problem: CODE 17 and also I have %CO & %HC very high i nthe smoke of the car. Also I have replaced the O2 sensor and I have the same problem.

Best Regards.

Luis
 

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Outstanding Contributor
2003 SL500, 2003 SL55, 1998 SL500, (2) 1991 300SLs
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I mean, I don't know where to test continuity of the wires from the oxygen sensor, to...where?
You remove the electrical connector to the fuel injection controller and measure resistance between it's sockets #13 and #32. It should be infinite. Then you measure resistance from #13 to the socket to which the oxygen sensor's black wire goes on it's electrical connector. It should be less than 1 ohm.
 

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1992 500SL 129.066
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124 Posts
Hello bobterry99,

sorryo ,could you share some images about what you said it, because I can not understand, I know where is the fuel injection controller, but i do not know where is the socket 13 and 32.

Best Regards and Thank you.

Luis
 

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2003 SL500, 2003 SL55, 1998 SL500, (2) 1991 300SLs
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1990 R129
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The check engine light came on, on my 91 500SL, and i checked the code with the self diagnostic pushbutton and it gave me code 17. Code 17 is according to the CS1000
Fault Code Scanner pdf "Oxygen sensor signal wire shorted to positive or ground". I installed a new OEM Oxygen sensor and reset the code. The CEL went away for a day or two but came back again. Again with code 17. Any ideas what the problem could be?
I've posted before about this code 17...reset the code, and 50 miles later, it pops back on again.
I've installed 2 oxygen sensors already. When CL comes on, fuel mileage goes WAY down, and smelly exhaust.
The only thing I can think of is the plug for the sensor, which is under the passenger seat.

My bogging problem was unrelated to the oxygen sensor, and was cured with a new EHA valve. HOWEVER, the new EHA was not calibrated well for this engine, and caused a lean condition. Richened up the EHA valve about a half turn in, and it runs pretty good.
 

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This fixed my code 17 on 92 500sl. Get a multimeter that can read duty cycle, probe pin 3 on the data link connector by the drivers side front fender and ground your other lead. The adjustment screw for the distributor is right on top, in front of the distributor. Hold rpms at 2500 and begin to adjust until duty cycle drops to about 50 percent. Once I did this my oxygen sensor started reading just fine, my idle got better and cold start ups are also better.
 

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Mercedes 380sl 1990 Mercedes 190E 2.6 1988 Mercedes 300ce 1982 1995 Mercedes E320
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This fixed my code 17 on 92 500sl. Get a multimeter that can read duty cycle, probe pin 3 on the data link connector by the drivers side front fender and ground your other lead. The adjustment screw for the distributor is right on top, in front of the distributor. Hold rpms at 2500 and begin to adjust until duty cycle drops to about 50 percent. Once I did this my oxygen sensor started reading just fine, my idle got better and cold start ups are also better.
Wow this worked for me, thanks so much
 
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