JD 850C MISTRACKING GOING IN CIRCLES

[GUNNER88]

hello all, does anybody know if a hydrostatic 850c will need a different program than service advisor to read the transmission controller? its spinning in circles, I believe it to be a speed sensor but when I hook up to it, I can not read the transmission computer, (it reads N/A) I can although read the engine controller, I have no codes on dash or alarms. THANK YOU FOR YOUR HELP IN ADVANCE. 850C SN915872

 

[mg2361]

Welcome to HEF GUNNER88! Unfortunately no, there is nothing to connect to that "C" series TCU to view readings, only a cable for reprogramming. Try a calibration procedure. If there is an issue it will show a code that will lead you in a direction. Did you go into section 9015-35 and look for "access display monitor codes"? You can get stored codes that way.

 

[mg2361]

I have a "C" series coming in the shop tomorrow. I will double check the connection issue with Service Advisor. What version of Service Advisor are you using?

 

[GUNNER88]

yea youre right you cannot go through service advisor, I have 4.0

 

[mg2361]

One of our tech's tried and was able to see the TCU and get into readings, but the readings couldn't read anything. We use SA 5.

 

[erickson_ryan]

I have a similar issue if someone thinks they can help 1997 jd 850c sn810865. Dozer will randomly decide to engage the right track in the forward direction only. I can't control the dozer in any way. I just had the tcm refurbished (does this need to be reprogrammed to work properly) I can't go past the decelerator part of the recalibration procedure. Rpms won't display on the monitor either.

I have a butt load of sensor voltage readings among some other useful info I can post if someone needs that to further help me.
Thanks!

 

[mg2361]

Welcome to HEF erickson! Next time start a separate post instead of piggy backing another. Thanks for posting a serial number.

When it randomly moves does that happen only when the park lever is released? Or does it happen with the machine just sitting there in neutral after you had stopped moving, then all of the sudden it moves? Any codes?

I would think yes, the TCU may need reprogramming if any hard parts (chips) inside were replaced. However I am skeptical of any TCU (or any other controller) refurbishment. I don't know of any establishments that deal with heavy equipment controllers, but that doesn't mean there aren't places out there that can. I'm curious, who did you use? I would think you need the dealer to come out and perform a programming before we move on to eliminate that.

 

[erickson_ryan]

The dozer will only move when taken out of park, and it doesn't happen every time. It's very random. If it does ever move when taken out of park when it stops by itself it won't move again.

No codes, I fixed everything pertaining to the ones that popped up. Only one that might still be left is f621 but I adjusted the right track speed sensor so not to concerned about that.

I used acs industrial services out of north Carolina to fix the tcu. They guaranteed it with a 2 year warranty so I hope they knew what they were doing

While trying to recalibrate the tcm. Holding the button down as well as the decelerator pedal, start the engine. Let the button go. Screen will pop up with tcu software 600, then 11, then p, move the park lever down and 45e pops up. 45e is supposed to stop flashing before you let up on the decelerator pedal but doesn't stop flashing until you let off the decelerator pedal. You can then progress no further than this.

All the rotary sensors for the controls all seem to be within spec range but reversed of what they're supposed to be. (So forward voltage reading should actually be reverse and vise versa)

The only thing that doesn't seem to work from what I've found is the rpm read out. The hydrostatic speed sensor tested within spec, pin 17 to the back of the monitor tested the proper 14v. That leads me to believe the monitor is screwed up or something with the tcu?

 

[mg2361]

Did you measure AC voltage at pin 17. The monitor is measuring the frequency from the "W" terminal. If you have a meter that can read Hz you can see if that changes with the engine rpm. Did you check the speed sensor that is mounted in the side of the hydrostatic pump? That is where the TCU gets it's speed from for calibration.

 

[erickson_ryan]

Yes measured ac voltage at pin 17. Came out to 14v. Did not think to measure the hz, I'll have to try that out tomorrow. Yes I checked the speed sensor on the hydrostatic pump as well and it tested within spec.
Hydro speed sensor: red-black= 5.03 volts
Red-white= 4.73volts-285.1mv
Red-white, engine start= 2.446 volts

I have a Deere tech scheduled for tomorrow to come reprogram the tcu.. hopefully this will fix my issue?!?

 

[erickson_ryan]

Update: all the wiring, sensors and computer check out. Ajusted the rpms back in spec range (helped me get further in the calibration process) lifted the dozer off the ground (seemed to allow the tracks to slightly turn as required in the first half of the calibration, well the right one anyway) to go through the recalibration sequence. Was able to get through the first half of it but no further.

The dozer only wants to work in 3 gear and the left track intermittently works. The transmission filter restriction light now comes on. Gonna replace the filter first and see where that gets me.

 

[mg2361]

For what it is worth, we just had an 850C in the shop with a severe mistrack to the left and no codes (which is highly unusual). The right speed sensor was the issue. New sensor and calibration...works like a dream.

 

[erickson_ryan]

So I changed the transmission Hydraulic filter. That fixed 90% of the problem. Both tracks will operate now. When I try to recalibrate the tcu I can make it all the way to where you push the cal button on the controller again and then it'll flash (LD) can't make it past this part. When I start to drive it, it'll flash a f621 code which is the right track sensor. I tested the sensor and it tests good! Maybe it needs to be adjusted some more or the recalibration needs to be fully completed. Also when the dozer is jacked up and in calibration mode when you move the stick to forward and reverse the left track will rotate a full revolution but the right track only moves like an inch?

So here's the other major issue after operating the dozer for say 20 min it just quits moving. I can let it sit for a little bit start it back up and it'll usually move again. Kinda lost on that one

 

[mg2361]

I tested the sensor and it tests good!

How did you test the speed sensor? I have seen many sensors pass voltage/ohm checks on those machines and still be a bad sensor (things change under operating conditions). Swap the left and right speed sensors to see if the code switches to the left side.

Also when the dozer is jacked up and in calibration mode when you move the stick to forward and reverse the left track will rotate a full revolution but the right track only moves like an inch?

Will it do that when in normal operating mode?

 

[erickson_ryan]

Sorry it's took me a while to get back to you mg2361.
I tested the sensor according to the technical manual. Red to black wire I received 5.02v...black to green was 4.71v in reverse and 274mv in forward...white to black was showing alternate values of 4.71v and 274mv... machine at constant speed on white and black was showing 2.74v.
Everything checked out here so the next thing I did was adjust the sensor. The f621 code went away at this point and is throwing no more codes. It only flashes letters LD at the end of the first half of calibration.
I then went to test the left track sensor on black to green wire and in reverse it showed 313.9mv and forward it showed 309.2mv I tried adjusting the sensor to get it to read between (4.6-4.8v) in one of the directions but no luck so I'm pretty sure this is my issue. (Gonna try to pick up a sensor tomorrow and see if that does the trick)

For your second question it tracks somewhat normal in operation mode, you can obviously tell it doesn't track straight and it only seems to work when the transmission is in high gear. The 2 lower gears don't really do anything besides minimal movements.

Also I replaced both fuel filters and the alternator because it was weak at 24.2v and now the dozer will continue movement after about 20min and doesn't all of a sudden stop.

My question for you is when y'all had that 850c in the shop and calibrated it how much did the tracks turn when the machine was at 1500rpm and the stick was pushed in forward and the reverse? Very minimal or about a whole revolution?

 

[mg2361]

During the threshold portion of the calibration they typically will not turn at all until the controller ramps up the milliamps enough to turn the tracks slightly (1 -2 track pad lengths, if that). That is usually enough for the speed sensor to send the feedback the controller is looking for. Your tests do indicate a speed sensor issue. Take care of that and try to calibrate again and we will see where we need to go from there.

Are both tracks turning when placed into FWD during that part of the calibration? Does the LD (L = rear pump left motor PCP, D = left motor speed sensor) show up after this point or when your done performing the FWD and REV threshold calibration? If you count the flashes of the light on the dash are the number of flashes approximately the same in fwd as in rev until the track moves?

Re-reading the original post I see that your machine had moved without command, correct? Is it still doing that? Might want to perform a flushing procedure which is in the manual TM1588, section 9026-25.

 

[erickson_ryan]

Ok so mostly good news this time. As you stated the bad track sensors don't always throw a code as this one didn't just found out through the volt test. But it was in fact bad. I changed it out and now I can calibrate the dozer all the way to the end at which point you press the cal button for the last time. If the process was successful it's supposed to display 1111 well mine displays FR. Any clue what that might be? The dozer will now operate in all transmission speeds it just tracks a little off. (The springs for left and right in the joystick are pretty worn and you have to do all this by feel, could the joystick not be in it's proper position causing this last little issue?)

After the speed sensor replacement during the threshold portion of calibration both my tracks now barely turn so that checks out with what you said!!

Previously the both tracks would turn during calibration, the left would go first for a full revolution then the right would turn just slightly and the LD only popped up after this step was complete.

That issue I originally had with it moving by itself was the 31 pin connector that connects rops harness to the engine harness. I cut it out and replaced it and that fixed that issue....this was a fire dozer originally and I had to replace alot of wiring.

 

[mg2361]

If the process was successful it's supposed to display 1111 well mine displays FR. Any clue what that might be?

Is the Fr to the left in the screen or on the right side of the screen? Or does it show FrFr? Basically an Fr at the end of calibration means the full speed calibration failed. Try it again. Sometimes it takes more than one attempt to complete successfully.

 

[erickson_ryan]

Good question, I didn't really pay attention to the placement of it, but I wanna say it was to the right side and just a single FR.
Although during the full speed calibration I did notice the left track got to spinning a bit faster than the right.
I'll get back out there tomorrow and give it a few more tries! Thanks