JD 850-C II LT Transmition Issues

Hello to all.
I'm new here and this is my 1st post.
I live in Mexico, and I'm trying to sort out some issues on a 850c II LT dozer that had some electrical wiring issues and didn't move after that.
Serial number is: T0850CX917056
I checked wirings and service repair procedures according to manual an all seems fine now. No codes pop out when we try to move the machine.
The tracks move forward but in a very slow speed and when i try to do the calibration procedure, the display shows number 800 1st and then, number 10.
According to manual, it should show 45E flashing and then it should stop flashing so that we can go to the next step but it doesn't stop flashing.
Anyone could help me out with this issue?
Another thing i would like to know, is how much voltage the TCM should send to the PCP valves to activate them? Service manual only shows to measure resistance but i don't see anything about voltage and i would like to know to see if this could be a TCM issue or not...

Thanks

Welcome to HEF Ricardo!

Do you have the correct calibration procedure?

I have service manual for 750c abd 850c, and it speaks about calibration procedure for 700 software and above. So i assume I'm using / doing the right thing...
I just tested 12v directly to the PCP valves, and it works, so I'm thinking that for some reason the TCM is not sending the right voltage to the PCP but i don't know if the calibration will solve this...

For starters, voltage checks of the PCP's is not accurate. They are pulse width modulated, so using duty cycle is the only way to check if a command is being sent to them. However, there is no spec for this.

800 is the software version, 10 is a model designation.

So I have a better understanding of what is happening, you hold the CAL button on start up and release after 5 seconds, 800 (software version) appears, the 10 (I think model designation) appears, then the letter P appears, correct?

You lower the park lock lever, then the 4E appears flashing. You then press the decal pedal to the stop and the 4E never stops flashing. Is this correct?

mg2361 said:

For starters, voltage checks of the PCP's is not accurate. They are pulse width modulated, so using duty cycle is the only way to check if a command is being sent to them. However, there is no spec for this.

800 is the software version, 10 is a model designation.

So I have a better understanding of what is happening, you hold the CAL button on start up and release after 5 seconds, 800 (software version) appears, the 10 (I think model designation) appears, then the letter P appears, correct?

You lower the park lock lever, then the 4E appears flashing. You then press the decal pedal to the stop and the 4E never stops flashing. Is this correct?

Click to expand...

About the PWM signal you say, we used a scope to measure this, but there was no signal wave or pulse and there was only a 0.5v max constant voltage when moving the lever.
About the calibration procedure. Yes, you are right up to the point of the P that shows in display. When i move the Park Lever down, it shows 45E flashing, and according to manual i need it to stop flashing and then i can to the next step (as far as i understand), but it never stops flashing.
I tried to do the procedure even with 45E flashing, and (can't remember exactly now) the 4 and 5 goes away, i stay with the E but it never goes to the other step on display to calibrate the Lever, and no code is displayed...
Not sure if it's me doing something wrong or not...

Ricardo Oliveira said:

About the PWM signal you say, we used a scope to measure this, but there was no signal wave or pulse and there was only a 0.5v max constant voltage when moving the lever.

Click to expand...

We are going to ignore this for now.

I would check the decel voltage adjustments to make sure they are in spec. Make sure the decel pedal is all the way up against its stop when the throttle lever is at fast idle position. Does the engine rpm show in the monitor, and correctly when compared to hand held tach? The "E" not going out might indicate an engine speed sensor issue.

I just checked the decel voltage according to manual and it's all ok. 5v ok, and 3.78v with pedal released and 1.28v with pedal fully pressed down. Voltage goes up and down according to pedal position.
Rpm shows in display, and they seemed to match engine. I don't have the hand tach to compare values.
Today I can't do much on the machine, because i need to go home and it's a 300km drive each way, so only next week i will be back here to continue this.

Just tried to do the cal again, and same result.
4E starts flashing and no way it stops flashing.
I tried do the Lever (1st) procedure and the 4 goes away, but the E stays and it will not go to the "267".
We found a 750C here in town with also a not moving issue, but only on Tuesday we will be able to go there and try the computer or see if the software is the same. Part number is the same but soft might be different...
Anyway, i really appreciate your help and will be posting all i find / check to sort this out...
Thanks...

Just tried to do the cal again, and same result.
4E starts flashing and no way it stops flashing.
I tried do the Lever (1st) procedure and the 4 goes away, but the E stays and it will not go to the "267".
We found a 750C here in town with also a not moving issue, but only on Tuesday we will be able to go there and try the computer or see if the software is the same. Part number is the same but soft might be different...
Anyway, i really appreciate your help and will be posting all i find / check to sort this out...
Thanks...

Hello guys.
So, i just want to share some inputs on this dozer issues:
It turns out that we where not being able to do the transm. calibration because of the speed sensor on the front pump. I think its the B14 sensor on the wiring diagram...
We interchanged sensors between b14 and b16 and we where able to start calibration, but with the F635 code, so this confirmed the speed sensor fault...
We got the sensor in place and i was able to do the calibration procedure, but for some reason the "E" letter always shows in display...
Anyway, by doing this calibration procedure and even with the "E" letter in display, the machine seems to moves fine.
We have the machine lifted from the ground to do this repair, so the final test will be after all fluids and filters replaced, take it to the field and see how it goes...
I waals also able to do a quick measure on the voltage for the valves solenoid's and i saw that it will go from 0.5v up to 4.3v (in this case) depending on the speed you use/setup on the machine...

I really appreciate all the help given here...
Another question I have is, can someone tell me the transmission and hydraulic oil we should use on this machine?

Thanks.

Ricardo Oliveira said:

can someone tell me the transmission and hydraulic oil we should use on this machine?

Click to expand...

While the operators manual will probably state engine oil, engine oil has been replaced in hydraulic/hydrostatic systems with Deere's Hydrau hydraulic oil. I highly recommend using the Hydrau.