Have a 1990 300e 2.6 gas. Has a push button code reader. It flashed 17 times which I read to mean bad Oxygen Sensor. Code 17(Oxygen Sensor signal). I replaced the oxygen sensor and cleared the code and the trouble light keeps coming back on. Any ideas on what might be going on or the next thing to do. Thank You for your help. Roger

Whenever this happens to me, I have to go back and check my work.

Did you use a generic sensor with a splice or an OEM?

Oem bosch with exact same connectors.

On that car if the mixture is mis-adjusted where the O2 sensor can't function you will get a code OR if the O2 sensor heater doesn't get 12V while running you will also get that code!

With the car running you MUST have battery voltage at the 2 white wires to the O2 sensor heater, don't disconnect wires to measure. Just slide the connection back to get to the male pins.

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If the heater voltage is not present, check wiring under passenger floor mat area.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

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I checked the voltage. I have 12 volts at the white wire that goes to the red/black wire on the oxygen sensor and no volts at the white wire that goes to the brown/black wire at the oxygen sensor. Is it correct that I need 12 volts at both wires and where does the brown/black to white go if anyone has a schematic.

The 12 volts is the heater. The signal voltage will be about 455 milliVolts at ideal stoichometric. Look for something like 100 to 700 milliVolts from the sensor. I don't know the color codes of the sensor wires.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

Everything checks out as far as voltage. The only thing I can't check is the fuel mixture other than the car runs great and gets great gas mileage. Am I reading the code correct that 17 flashes is a bad Oxygen Sensor and is there anything I can try next other than taking it to someone to check the fuel mixture. Thank You

Are you saying that you have tried to get a fuel mixture reading from diagnostic connector X11 (round capped component on left fender)?

With multi-meter on pins 2 and 3 you should be able to get a duty cycle/fuel mixture reading. You can convert volts to duty cycle but easier with a duty cycle reading on meter.

It sometimes happens that the O2 sensor only starts functioning correctly after the fuel mixture is adjusted a bit.

Thanks for the help but no I haven't checked the fuel mixture because I don't understand how to or adjust it. If you can explain how to read the duty cycle with a multi meter and adjust mixture I will give it a try.

http://www.landiss.com/mixture.htm
see 25-27 here: http://www.w124-zone.com/downloads/MB%20CD/W124/w124CD1/Program/Engine/103/07.3-1100.pdf

Adjust at operating temperature. Need a long hex drive 3mm I believe.

Disconnect and cover regeneration valve with electrical tape. Leave air cleaner in place. Use hole in air cleaner to adjust. Use very small adjustments (1/8 turn is a lot). (Removed air cleaner or not covered regeneration valve would be same as vacuum leak and you are setting air/fuel mixture and would also be about 9-10% off.)

Place multimeter red in pin 2, and black in pin 3 of X11 for Mercedes duty cycle calculation. Set mixture adjustment to average 47% duty cycle at idle. Look at duty cycle at 2500 rpm's and see if it is within 10 points. The reading should fluctuate somewhat rapidly as this is in response to the O2/lambda sensor relaying good info. If no duty cycle reading on your meter the math calculation is in first link above.

It should be smooth running at idle and responsive just off idle and within 10 points at idle and 2500 rpm.

You can adjust for your best performance but just keep it within the 10 points. Counter clockwise adjustments are lean. Keep up with where you begin and all adjustments made so you can put it back exactly where you started if you decide to.

Roger,

Have you solve your car's problem.

If so, can please post some info on how you solved this problem?

Thanks in advance.