First off, let me start by saying, I am by no means a heavy equipment mechanic. But I am fairly mechanically inclined and typically am capable of figuring things out/fixing them myself if I mess with it enough This will be lengthy but i’m trying to give everything i know and have done thus far. Any help is greatly appreciated. So, let’s get into it. John Deere 450J: SN: 1TO450JXKCD218918 1 Active Code: TCU 523108.14 17 Stored Codes: 908.12, 907.12, 97.3, 1638.3, 523577.9, 523578.9, 522444.4, 2661.4, 2660.4, 522448.5, 522450.6, 522449.5, 96.3, 157.17, 91.9, 522447.6, 522447.5 (I know holy sh*t) This dozer is a buddies. It has pulled left and had speed sensor codes for a while to my knowledge. I am not entirely sure the exact length of time but it has been ran that way for quite some time. A friend of ours (JD mechanic at the time worked on the dozer several years back and i believe did a null adjustment on it and got it tracking pretty good and straight but it still had a slight left hand pull. Probably had 2-300 hours put on it then it sat for almost a year and was not ran. I bought a piece of property and have borrowed the dozer and used it for several hours as well with it pulling left just mainly cleaning up brush and small trees. No heavy pushing or abuse. The dozer sat for 3-4 months throughout the winter and was essentially untouched. Come spring this year i began working on the property again. Dozer fired right up and i put it to work. I probably had 2 hours on it when the current issue occurred. As i was tracking back for another push of dirt the dozer locked the right hand track and on its own threw full power to the Left track. Took off spinning right. No matter the position of the drive joystick it sends juice to the left track only. It should also be noted that upon start up if you do not throw the park brake lever down that the dozer will stall out because the pump is loading up trying to send fluid to the left track. I called that same friend (unfortunately he no longer works at deere, but he does now run his own service truck and has access to John Deere service advisor with all the manuals) he inspected the machine and narrowed it down to the PCP. You could unplug PCP and machine would idle just fine. As soon as you plugged in PCP machine would die unless you immediately threw the park lever down so that the left track was free to spin. 1550 dollars later machine has a new PCP… No dice. Didn’t fix it. Didn’t change a thing matter of fact. I can tell my friend that’s worked on it a few times really is not interested in messing with this thing. Nor does he have quite the access to parts that he used to at deere where he could swap say a new TCU on to see if that fixed issue or not. I myself located the speed sensors at back of machine and managed to get enough slack in harness that i could plug left to right and right to left. Same issue. Left track still wanting to spin on its own with right track locked tight. That leads me to believe that something internally on the pump must be stuck. Prefer not to have to call a John Deere service tech out but it’s looking like that may be what has to happen. Any tips and advice is much appreciated. I’ll also add this machine is an open cab and has spent likely its entire life but definitely last 6-7 years outside in the elements. The TCU doesn’t look the greatest but the connectors are clean and corrosion free.
Welcome to HEF ian8or ! Are any of those stored codes active while the machine is acting up? Do you know how to clear the codes?
The only active code for the short little bit i can get the machine to run while it’s acting up is that TCU code: 523108.14 I am not sure how to clear the codes.
Also i do not know the proper term for it but the small “switch” that is on the PCP i can manipulate and you can really hear and feel the machine/pump whine. It will spin in a circle for about 8-10 seconds and then die out. That side drive motor engages immediately so it’s not even enough time for the machine to be able to get the idle up before it just bogs and stalls out.
Figured out how to clear codes. Cleared them. No stored codes left, just the one active that i listed above.
That is a pump speed sensor calibration incomplete code. That will not cause the machine to turn in circles on its own. You mentioned that with the PCP disconnected, the machine will sit still and idle fine, correct? You also mentioned that the wires from the front pump and rear pump were switched and the issue remained with the same track, correct? Has anyone checked the PCP differential pressure? The PDCV differential pressure?
Correct. The PCP that is directly in your line of sight when you pull the floor pan off is the one that was replaced. I would call this the “Rear” pcp. If you unplug it the machine will sit and idle. You plug it in, pump loads up and stalls the machine. I swapped the wires between left and right wheel speed sensors at the back of the machine. This did not make the problem swap sides. Issue stayed the same. No, the PCP differential pressure has not been checked or PCDV. I was told by my friend a special set of gauges was needed to do this with a special transducer. Is that accurate?
Swap the PCP connectors from the front pump to the rear pump. Does the issue move to the right side? You should use a differential pressure gauge for accuracy, but it can be done with two gauges if you confirmed they read the same.
I am not near dozer currently, but from what i remember the two wire Deutsch connector that’s in the harness doesn’t seem like it would have enough slack to reach the opposing PCP. I will attempt to swap them though and report back. What is the testing procedure for the differential pressure? What values would i be looking for ? I see in other forums where you’ve commented that a set of hoses connected to a Tee with shut off valves on each side can be used. Would that apply here as well?
Like this
Perfect. Check your messages.
You stated in your post that if you unplug the PCP the machine will idle and not stall out. Is this statement correct? If this is the case i would thank you would not have a mechanical problem in the pump or the pump displacement control valve. I would suspect a wiring issue or TCU issue. I have seen cases where a bad harness has juiced up the PCP with battery voltage which creates a very dangerous situation unless the operator is savvy enough to turn off ignition switch.
I agree with Steve. You have an electrical issue.
SAFETY ALERT if you are working on one of these dozers in this condition and has a lot of hours the park brake disks may be worn enough that the machine can drive right through the park, been there experienced that lucky to still be here. Keep all by standers at a safe distance. One thing you can try if you have a clear area let the dozer continue to go in circles to see if the TCU can shut the hydro down, it should if it is working properly.
Or, if you can, block up the machine so the tracks are off the ground.
That is correct. I have not had time to mess with the machine here the past couple of days. I have ran two brand new wires and new deutsch connector with new pins direct from the TCU on the fender right out of the harness straight down the to the new pcp. Still the same issue. That at least in my mind eliminates a wiring issue. So bad TCU? What kind of voltages would i be looking to see on the blue T38 and T41 while the machine should be in a neutral position? What voltage should i see in Forward?
I not sure but that may be a milliamp signal to the pcp. Unplug both pcp and do a comparison test. Have you ever tried to perform a TCU calibration procedure? The TCU can do some weird crap if calibration was not completed. Does the window in the TCU appear cloudy or have moisture behind it. Could you send us a photo of the TCU. How many hours on the dozer.
Check your messages.
Just one more thing as far as safety- most typical brass ball valves do not have a maximum working pressure range to be used in any hydraulic circuit. I have seen them used and fail. McMaster Carr is just one of many vendors for affordable steel ball valves suitable for hydraulic applications.
This doesn’t pertain to this machine but this is funny. One of my old coworkers from years ago called had a 240DLC that had set all winter and had no hydraulics. Said he manually checked pilot pressure and was good. Had him go into monitor check pilot pressure for a couple functions had none. Told him probably some furry critters had spent the winter in the panel under the cab an chewd the wires in too going to pilot shut off solenoid. This will be the third time I have seen this.
Friggin acorns!
Update time! After several hours of fooling with this dozer. Back probing and swapping connectors, jumping wires, checking voltages, resistance… etc. Even went as far as to split the TCU open and replaced two of the capacitors that are known to fail.. with no luck. Member Steve Austin that has posted on this thread previously is fairly local to me. He came out and saw the machine. He’s a wealth of knowledge to say the least and between he and I we finally came to the conclusion that it had to be internal of the TCU. I started by pricing a brand new TCU from Deere. $5000. Only 3 left in the country available. Didn’t want to have to go this route but it was in the list of options. From reading on other forums Id read about ERD. ERD is an electronics repair company out of North Carolina. They specialize in fixing things like this TCU. Long story short this is the route I chose to go. Mailed it off on a Monday via UPS, they received it Wednesday, got a call from them thursday confirming they received it and they gave me a quote for repair. $1990. Lead time is 19 days.. but the following thursday they called me letting me know the unit had been repaired and they were ready for payment. Total came to $2050. Paid and they had it shipped same day. Received the unit today (Saturday) at 1:30PM. 10 day turn around time between me shipping, them repairing, and them shipping back. Pretty impressive. They have an in house test module for these TCUs that is able to simulate the TCU being hooked the the actual machine. In that module they’re able to actually receive feedback from and send commands to the TCU. That way they can make an accurate diagnosis and verify repair. Needless to say they know what they’re doing. Attached in the photos you’ll see the freshly blasted and painted TCU along with the description i provided to them when i sent the unit in as well as the description of the troubleshooting they did and ultimately the parts they replaced to fix the unit. I plan to re install the TCU later today and run calibration. I will update one more time after I do that.