Duty Cycle error codes - Page 2 - Mercedes-Benz Forum
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post #11 of 20 (permalink) Old 02-19-2019, 08:56 AM
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Mmmm page not found on all of them...

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post #12 of 20 (permalink) Old 02-19-2019, 11:15 AM
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...IMHO one of the best stories on the forum today is Bauk18's about changing a fuel filter and now no start.
Thank you, I do my best

How hard can it be?
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post #13 of 20 (permalink) Old 02-20-2019, 04:31 PM Thread Starter
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Mmmm page not found on all of them...
I guess I'm technically challenged!

But better yet read Bauk 18's thread. All of the links are in there. That's where I got them from.
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post #14 of 20 (permalink) Old 02-21-2019, 06:48 AM
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Thx a lot! :-)

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post #15 of 20 (permalink) Old 02-24-2019, 02:21 PM
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Originally Posted by Bauk18 View Post
Yes, you measure DC on pin 2 and 3 of the X11 diag. socket at idle. Ignition on, engine off gives you also a static reading, 70 or 85% (85% = California spec). It's recommended to start with this reading as you can check that your DC meter is reading the off-time of the DC and not the on-time. If you see 30 or 15% you know you are reading the on-time which will give you the wrong indication of a problem.

Duty cycle meter:
Some duty cycle meters show the percentage of the square wave voltage’s ‘on’-time, and others show the percentage of its ‘off’-time. In case of the KE-Jetronic the duty cycle value refers to the square wave voltage’s ‘off’-time. A meter which shows the ‘on’-time would, for instance, read 53% instead of the relevant 47%.
If you’re not sure which version your meter is: With ignition switched on (engine not running) the duty cycle should be about 70% (California: 85%). If the meter shows about 30% (California: 15%), it’s probably the wrong version. And if, while the engine is running, the fluctuating duty cycle drops when the adjustment screw is turned cw, it’s the right version.
So my Fluke 87V meter reads 30.2 with ignition on engine off (pic one). So I am reading on-time not off-time. With engine running I get a duty cycle of 50.2% second pic. Does this mean my off-time reading is actually 49.8%? Is it valid to use the on-time percentage minus 100 percent? If not, how do I get the right version as noted by HD? Should I just tweak the adjustment to get to 50.0%? Is there a reference to a thread that explains this? Thanks for the advice.
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post #16 of 20 (permalink) Old 02-24-2019, 02:34 PM
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So my Fluke 87V meter reads 30.2 with ignition on engine off (pic one). So I am reading on-time not off-time. With engine running I get a duty cycle of 50.2% second pic. Does this mean my off-time reading is actually 49.8%? Is it valid to use the on-time percentage minus 100 percent? If not, how do I get the right version as noted by HD? Should I just tweak the adjustment to get to 50.0%? Is there a reference to a thread that explains this? Thanks for the advice.
To be sure what you Fluke is reading, I would suggest to calculate the DC manually with engine OFF / ignition ON with the following formula:

The voltage is converted to duty cycle according to the following formula:
duty cycle [%] = [1 - (Vp3 / Vp6)] * 100
Vp3 = voltage between X11 port 3 & port 2 (or ground)
Vp6 = (battery) voltage between X11 port 6 & port 2 (or ground)
([email protected])

If you get the same % you know your are good, if not then your are indeed reading on-time, -100 gives you off-time, but easier the switch to off-time on you Fluke, as it's a Fluke I can not imagine this is not possible.

EDIT: press the continuity beeper tone button to switch between on and off time.

Secondly, with [email protected], was your % fluctuating?

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post #17 of 20 (permalink) Old 02-27-2019, 03:30 AM Thread Starter
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See what readings you get if you put the common probe into pin #3 and positive into #2. I did this with my Klien meter and get off time readings. But if I am mistaken please set me straight as I just got my meter, my first ever, for Christmas. So I could be wrong.
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post #18 of 20 (permalink) Old 02-27-2019, 05:56 AM
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Originally Posted by Bauk18 View Post
• 0%: problem with the meter
or diagnostic coupling (X11)
or too rich setting (beyond the EHA’s ‘leaning limit’)
• 10%: TPS (throttle position sensor), throttle fully closed signal
or (if at 2.000 rpm) no/false supply voltage to POT (air flow potentiometer)
• 20%: TPS, ‘throttle fully open’ signal
• 30%: CTS (coolant temperature sensor)
• 40%: no/false output voltage from POT
• 50%: o2 sensor (aside from not having reached its operating temperature yet)
• 60%: car speed signal (displayed during driving or engine still running after driving)
• 70%: CPS (crankshaft position sensor) or EZL (electronic ignition module)
• 80%: IATS (intake air temperature sensor)
• 95%: micro switch of throttle linkage (6-cylinder engines)
• 100%: problem with the meter
or diagnostic coupling (X11)
or ECU ‘N3’ (missing connection to voltage supply or to ground)
or OVP (overvoltage protection relay)
or o2 sensor signal (short to ground)
or too lean setting (beyond the EHA’s ‘enriching limit’)

Credits to H.D.
What is the meter reading that all is OK?

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post #19 of 20 (permalink) Old 02-27-2019, 09:17 AM
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What is the meter reading that all is OK?
When the reading is not static.

If you have a fluctuating reading you know that the "inputs" like coolant temp, 02, full throttle etc are transmitting their values properly to the ECU and being properly received by the ECU, but do remind this doesn't mean you have a problem free CIS system, you can still have as vacuum leak for example, see my personal saga. :-)

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post #20 of 20 (permalink) Old 02-28-2019, 01:14 AM
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It's a pity they don't do hands on training + diag + repair either online or somewhere in the world. I found some in Germany, but in German and only for professional qualified mechanics of Bosch services. I wouldn't mind spending one week abroad if I get to master KE ie. Anybody has any leads?

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