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Old 04-05-2005, 11:53 PM
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dmorrison dmorrison is offline
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Join Date: Dec 2002
Location: Colleyville, Texas
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I have done fuel injector cleaner, Chevron Techron
I will try some more before I can get to this. it may help.

Today I did some more reading and amazingly the light came on.

OK this is what I figure with the #3 pin in the X11 connector.

If you use the Sears MM meter and get a number that is a multiple of 10. ( 0,10,20,30,40,50,60,70,80 or 90) You have a fault in one of the components.
If the value is variing then your getting the lambda input produced by the CIS-E computer.

Here are the values in the manual for the various fault codes

0% No voltage or ground at the diagnostic socket. Open in wiring of the diagnostic socket contact 3. lambda tester faulty. mixture to rich.

10% Air flow sensor potentiometer wongly connected or faulty. Possibly, fast idle speed

20% Full load contact wongly connected or faulty. 20% readout only if microswitch connected

30% Short-circuit or open circuit between CIS-E control unit and coolant temperature sensor or coolant temperature sensor faulty.

40% Open circuit or short-sircuit to air flow sensor potentiometer or faulty. Possibly, fast idle speed.

50% O2 sensor not operating or faulty. Open circuit

60% Not assigned

70% No TD signal (open circuit) at CIS-E control unit.

80% Open cicuit or short to ground. Altitude correction sensor fauity.

90% Not Assigned

100% Lambda setting too lean. O2 sensor faulty (short to ground). No voltage or ground at CIS-E control unit or CIS-E control unit faulty. Lambda tester faulty.

Here are the other pin outputs on the X11 connector based on the pin #

Pin Function
1 RPM signal, 0 to 12 V, 4 pulses per revolution. A frequency of 43.3 pulses per second corresponds to the desired idle speed of 650 RPM. (To check your tachometer you could measure the frequency at this pin and multiply by 15 to get RPM.) This signal is derived from the ignition amplifier and is synchronized with the low side of the ignition coil.
3 Lambda on/off ratio, 0 to 13.6 V, 100 Hz. This is not a replica of the output of the oxygen sensor. The "duty cycle" in Mercedes literature refers to the percentage of time this signal is low. Longer duty cycle (lower average voltage) = lean, shorter = rich.
4 Low (negative) side of the ignition coil. This is where to monitor the dwell angle of the electronic ignition amplifier, and is also a good place to view a reflected and attenuated image of the spark. This is about 50 VPP, safe for an ordinary oscilloscope.
5 Hot (battery voltage) in Run or Start, NOT FUSED! This is actually the positive side of the ignition coil.
6 Hot at all times, through fuse 2
7 Shielded cable from TDC sensor. This is not the same sensor which triggers the spark control unit, but it could be used in a clever circuit with pin 1 to measure spark advance.
8 Shielded cable from TDC sensor.
9 Shield for pins 7 and 8.

So I have that figured out so far.

I still have the second question that was not answered. The one about the N3 connection access.

"To trouble shoot the entire system the manual goes into connecting a pin access board to the N3 connector under the floor board in the 560SL.
By measuring voltage or ohms or amps of various pins you can determine the condition of the various parts on the CIS-E system.
Is this normally how it is done? Can you access the pins under the floor board, without the service manual equipment, or should I test the components another way.
This is located the the same manual 07.-.0711-121 page "



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1985 300D 264,000mi Son's new daily driver.(sold)
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