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ColdBlackWind

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May 26, 2023
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168
Location
Trigonia, Tn.
Pulled up diagnostics. I had one event around fuel leakage when I first got it but it was running out of fuel. Had one on water in separator. Drained that. The last two were related to drive motor speed. 2687-2 was first chronologically. E1CB3EB0-A733-428C-905E-82AB2739643E.jpegFC33438D-69AF-4BA3-B443-9F3D6D35ECBE.jpeg
 

Nige

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Jun 22, 2011
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G..G..G..Granville.........!! Fetch your cloth.
Had one on water in separator. Drained that.
I suggest that you should keep that bowl well-drained. The High Pressure fuel syustem on that engine DOES NOT like water.
I also suggest you need to drain water & sediment from the tank if you don't know when it was last done. There is a procedure for it in the O&M Manual.

Attached is the troubleshooting procedure for the 2687-8 Diagnostic Code.
NOTE the comment that even when the cause of the Code has been found and fixed the machine as to be driven for some distance to create a "good" sensor signal before the Active Code is cancelled.
 

Attachments

  • MID039 CID2687 FMI08.pdf
    240.8 KB · Views: 16

ColdBlackWind

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Trigonia, Tn.
I will dig into it Monday. No rest for the weary. With it throwing alerts in both sensors does that sound like a crimped or cut wires? Possibly through the window in the frame. Will I need to pull tractor assembly back to access sensors?
 

Nige

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G..G..G..Granville.........!! Fetch your cloth.
With it throwing alerts in both sensors does that sound like a crimped or cut wires?
No it’s only throwing a DC for one sensor. Both Codes you see refer to the RH #1 sensor. 2687 refers to the RH #1 sensor, 2688 to the RH #2 sensor.

There are 2 speed sensors in a common housing on each side of the machine.

It could be a wiring issue, it could be one half of the sensor has gone AWOL. Carrying out the tests in the procedure in order will indicate where the problem lies.
 

Nige

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G..G..G..Granville.........!! Fetch your cloth.
Apologies I should have made it clear that Codes you have (2687-2 & 2687-8) both relate to the same sensor that is one of two mounted in a common body. Attached is the troubleshooting procedure for the 2687-2 Code but you will find for the most part it is common to the one I posted earlier.
 

Attachments

  • MID039 CID2687 FMI02.pdf
    235.7 KB · Views: 8

ColdBlackWind

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May 26, 2023
Messages
168
Location
Trigonia, Tn.
Got it. Have to replace my Fluke meter. It has gone sideways on me for some reason. I will open the machine up and clean it tomorrow hopefully.
 
Last edited:

Nige

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G..G..G..Granville.........!! Fetch your cloth.
Make sure that your replacement DMM has the capacity to read duty cycle. You may not need it on this diagnosis but there are a lot of PWM sensors on that machine (e.g. these speed sensor, joysticks, etc) and the DC capability will surely come in handy at some point.
 

ColdBlackWind

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Messages
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Location
Trigonia, Tn.
Kinda Greek to me. I do good to read AC vs DC. Running 10 hours and working on it for days isn’t what I signed up for. But I will get through it.
 

Nige

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G..G..G..Granville.........!! Fetch your cloth.
Kinda Greek to me.
You'll find the duty cycle measurement (on a Fluke anyway) operates on the same key as frequency (Hz).
With the meter set to measure AC voltage press the Hz key once and the RH side of the LCD screen will show a Hz symbol.
Press the Hz key twice and the symbol will change from Hz to % which is how Duty Cycle is measured.

A short tutorial follows on what the output signal of a PWM sensor looks like............

The duty cycle of a PWM (Pulse Width Modulated) sensor is measured versus time. See the illustration below that shows what the sensor output signal looks like at 10%, 50%, & 90% of the sensor Duty Cycle. Note that the only thing that varies is the "ON" time (grey shaded area) vs the "OFF" time (white shaded area). There is no change in voltage on the signal wire.

The "height" (red arrow) of the square wave is proportional to the voltage in the sensor signal wire - not to be confused with the stabilized voltage supplied to the sensor by the ECM. That voltage does not change and it confuses the heck out of people when they measure it.

1685329125094.png
 

Nige

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Just curious if the sensors are working properly what dynamic are they monitoring and why?
They are monitoring the drive motor speed in RPM. The reason that there are two of them per side is in case one fails the machine will still move using the signal from the other. It's the same reason the engine has two speed/timing sensors, redundancy.
 

ColdBlackWind

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Trigonia, Tn.
Yes sir I understand they monitor speed but what is that signal used for? Does it have anything to do with two speed function, snail mode?
 

Nige

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G..G..G..Granville.........!! Fetch your cloth.
Yes sir I understand they monitor speed but what is that signal used for?
It is a feedback signal to the ECM so that, along with the position signals from the joysticks, and the signals from the ECM TO the hydrostatic pump solenoids, the machine ground speed can be controlled based on the operator joystick signal input. The propulsion system on this machine is 100% fly-by-wire.
 
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