Hello, a friend and I have recently purchased an older ex120-2 that has some hydraulic issues. When we bought the machine it would barely move and the pump area was full of soot from where the previous owner had been using it with a muffler pipe rusted off so all the exhaust was dumped into the pump area. We have since cleaned up the pump area and fixed several naked wires from age and probably exhaust heat and it has helped tremendously. You can use the machine somewhat but the hydraulics will intermittently get really slow and then might jerk and go full speed. Engine/fuel seems to be good and I don’t believe we have a full swash issue with the pump anymore after fixing naked/touching wires. Any direction would be greatly appreciated. We replaced dp sensor and that did not help issue
Hello,welcome to the group.there are some of the best deere/hitachi people on here that are willing to help maybe they will show up shortly. Iwill say this don’t throw parts at it some time old parts are better than new ,get the books / wiring diagrams for it make sure every wire in that area is doing what it should.then clear the codes run it check codes repair and repeat till you stop getting codes
Can I check codes without having the dr ex diagnostic tool?
Where would be the best place to buy the manual I need. I am new to the excavator stuff so I’m learning as I go. I have seen where people talk about there being several manuals
Yes you can get the codes by shorting two pins in the connector and counting the blinks on the led on top of the pvc ,I don’t remember which 2 you need the whole procedure from the manual. It is on here somewhere
Maybe somebody will chime in with a link to the correct manual I need soon. Today after we replaced the dp sensor with no change we removed the angle sensor to see if maybe the previous owner removed it and reinstalled it with the dot 180 out. When we removed it when checked power and ground and 5v reference and had all of that like it should but when we set tried to set the angle to 4.4volts we couldn’t get it and the pump seemed to be stuck at full swash making the machine nearly immovable it would black smoke and stall without atleast half throttle. Does this mean the angle sensor is bad? You can remove it and make the shaft change the voltage on the meter by hand but when you install it in pump you can only get 3.9ish volts and it is running under extreme pump load
You can check for codes using the red light on the PVC behind the seat. See the link to an older thread below. Post #14 shows how to enable the self diagnostic which sets a light flash sequence, (if there are any codes). HeavyEquipmentForums . . I believe the PVC is the bottom controller and EC is the top controller. Ignore the light on the EC. if there are any codes ,the light on the PVC will blink in a pattern of long and or short sequence.
The EX120-2 manual KM105E03 is out there . If you have trouble finding one, it’s available at the Deere Bookstore. John Deere - Technical Information Bookstore Welcome to John Deere C&F Technical Information Bookstore. This site contains operating, maintenance, and service information. www.johndeeretechinfo.com
Thanks I believe I found a KM105E03 manual. Thanks for the part number on that. I’m going to check for codes in the next couple days and will post what I figure out. If the top controller is the ec controller then it is flashing a red light but the flashes are not the same some longer than other is this normal operation?
Before the electrical plug is jumped, the light on the EC and PVC should both be flashing about once per second indicating they are powered ”on” . Once the electrical plug is jumped (ignore the light on the EC) , check the PVC light for long and short flash sequences indicating there are active engine and or hydraulic service codes.
Alright we got a chance to work on our machine today, we got a manual and checked codes by jumping connector in the cab, had a code for dp and pressure sensor on main pump. We had just installed a new dp but found out it was set to .4 volts out of the box so we adjusted that and reinstalled. The flow chart tells us we need a p sensor. Am trying to find an online place that carries them but I am not having much luck. Anybody know where I can purchase one of these? And after starting machine up with the dp adjusted we no longer have a full swash condition but the hydraulics are still slow but if you mess with the boom functions it might get fast for a couple seconds then get slow again. Is this a condition that a faulty p sensor can or could cause?
The two codes we pulled off the pvc were 26 and 27 by the way
Did you clear the codes and check the harness?
If the PVC is reading the “P” sensor / circuit as a constant high pressure , the PVC will command the hydraulic pump to a lower swash angle decreasing the pump flow. First I would prove the condition of that wire harness section if you haven’t already.
We did clear the codes and still have the code 27. We followed the manual and checked that the harness was good between the pvc and p sensor. I don’t know how to know if the p sensor is reading a high pressure the manual just says short circuit of the p sensor and/or harness. When we got the machine all three wires of the p sensor were naked and touching but we have fixed that just not replaced the sensor. Since it’s only 5 volts would the dead short be enough to have ruined the sensor when the wires were touching??
I realize without DrEx you can’t confirm if the P sensor is producing a high pressure output. I was only trying to suggest to prove the harness is good before investing in a “P” sensor. The two “ P” sensor part #’s listed in the parts catalog all sub to # 4436271 ,looks like it’s readily available OEM and aftermarket.
Gotcha I didn’t know if you knew of a trick to see what kind of signals the sensor was sending. Thanks for the part number for I will see if I can find one to get it ordered. I will post what the machine does after we get us a sensor installed
Dave can’t he carefully backprobe the signal/middle wire on the p sensor read voltage key on not running
I looked up that part number and it sends me to one that Friday parts sells. I’ve looked at that sensor and in the application section it doesn’t specifically list an ex120-2. Does anybody know if that is still the correct part for my machine??
Good call @ Shopguy. Per manual , Fault code 27 indicates that the sensing signal (input voltage of the sensor) is higher than 4.75V .
Per post # 16, the P sensor part # I quoted is 100% accurate for an EX120-2 . The (2) original Hitachi part # ‘s subbed to # 4436271 .
I checked that I have more than 4.75 volts but that’s just reference voltage right? Couldn’t I have reference voltage and still get a false output reading if the sensor is bad internally? Sorry for so many questions just trying to fully understand what and how it works. Is rhe pressure sensor just and on or off type sensor or is it a sensor that gives various readings depending on what is input to it?
Thanks for the info diesel Dave I’ll get one coming from Friday parts
Of the 3 sensor wires ,the one in the middle position is the signal wire back to the PVC. Under normal conditions the signal voltage back to the PVC varies between .26 V and 4.74 V depending on the hydraulic pump pressure. What @ Shopguy is suggesting is to back probe the middle wire with key on engine not running.
Should it be low voltage with key on engine off or is it just good if it’s under 4.75?
Key on engine off we have .04 volts on p sensor middle wire
I want to say low voltage , something above .26V You are back probing the middle wire with the harness connected to the sensor ? With that low of a voltage , fault code # 28 should be produced.
Yes middle wire is only .04v
Per the manual , Fault code 28 indicates that the sensing signal (input voltage of the sensor) is lower than 0.25V, and pos- sible cause may be disconnection of the harness be- tween the P sensor and the PVC.
Stall a cylinder and see what the voltage is also I would try another volt meter 1/4 volt ain’t much
Had some time to mess with machine again today. Replaced the pressure sensor and everything seems to be working well except the curl on the bucket. We removed the solenoid/valve made sure is didn’t look clogged and reinstalled. Manual says it should ohm out between 5 ane 23.2 ohm. Our solenoid reads 23.9 but so does the one above which seems to be fine so I don’t know where to go from here. There is no more codes for pressure switch but when I re checked codes it looks like I have a code 14 but I don’t see a code 14 in the manual. Help please!
What issue are you having with the bucket curl ? What solenoid valve did you remove and check ? I don’t see a code 14 listed in the EX120-2 or EX120-3 manual.
the bucket curl was so slow. Prob 10-15 seconds to only use half the range of the cylinder. So we unplugged the solenoid valve and and started machine and it’s curling normal speed now. It’s the solenoid that works the bucket curl for the pilot circuit I’m pretty sure. That block area has spots for 8 solenoid valves and on the engine side has two relief valve looking things.
After running the machine with that solenoid unplugged for 20 minutes or so the hydraulics for the tracks would get slow but you could get them back if you messed with the boom functions and vice versa. If you grab the pilot lines where the pilot filter is located back by the main pump, it’s like the line is hammering or pulsing when you are using any function. Seems to be a sharp hard pulse almost like it’s loosing pilot pressure in the line for a split second then slamming all the line pressure back.
I do not know if the pilot lines were pulsing before today I didn’t grab the lines while it was running until after we unplugged solenoid
I want to say the pulsing in the pilot line is normal. The pulsing is created by the (2) displacement solenoid valves (on the top of the hydraulic pump) being cycled on and off by the PVC to maintain a constant pump flow while you using a function.
@Newberryi , did you ever end up being able to get the pump displacement angle sensor adjusted to the 4.4 volts ?
No sir, the best I got was 2v with the original and the new angle sensor. I really don’t understand the system good enough to know what would be the effect of have an angle sensor that was only set to 2v? Would that tell the pump to pump more or less or does is tell the EC to tell some other sensor information? I’m kind of at a loss. I don’t understand why unplugging the solenoid for the bucket curl sped the curl up and I don’t understand how you can get track speed to get back to normal when operating the boom functions when it’s acting up. Any help or direction would be so much appreciated
You tried adjusting the angle sensor exactly as per the manual ? The small spring clip between the pump and the sensor is in place ? Are you able to achieve 4.4 V if you turn the angle sensor shaft by hand ? If all above is ok, maybe someone has limited the maximum pump swash angle by performing the electronic control bypass procedure. The procedure is from a Deere 490E operators manual but does apply to an EX120-2 as well. .
Definitely wasn’t aware of a procedure like that so it’s possible but what does that procedure do to the functionality of the pump? Seems like the machine is working properly most of the time but intermittent slow functions but can get them back if you mess with multiple functions simultaneously. If you put it in the locked position does it hold the pump at a specific angle and keep it there?
Can the machine operate correctly (meaning electrically for the variable pump displacement) if the machine no longer has the electronic throttle controls? Our machine has a manual throttle that was installed by previous owner and the step motor and throttle angle sensor are gone but all other things are installed and plugged in
The bypass procedure only limits the maximum pump flow , it has no affect on the minimum. You could try cycle timing the travel with the engine at full throttle, Work mode in M1 and in rabbit travel speed to get an indication if the hydraulic pump is capable of reaching close to maximum output. From a running start over 65 feet of flat ground the travel time should be approx 13-14 seconds in rabbit.
Yes the machine can operate correctly with a manual throttle in relation to hydraulic pump control. The EC and PVC controllers only look at the speed sensor located in the drive end of the hydraulic pump housing to determine if the engine is being overloaded and excessively pulling down.
I will check that but I believe we are able to get max pump flow. The reason why I think that is before we replaced the pressure switch the engine sounded like it was constantly under load when sitting still using no functions and when you would use a function it would bog the engine extremely bad and would black smoke. Could it do that and still not be at max flow?
I agree, it sounds like the pump is close to max flow. BUT the question I have is how come you are unable to adjust the angle sensor even remotely close to the 4.4V spec with pump at max flow during the adjustment procedure. If the angle sensor input to the PVC is truly only 2.0 V at max flow then the PVC has no clue what the pump shaft angle actually is.
When adjusting the angle sensor you look for 4.4v with key on and engine off right?
See adjustment procedure below , step #6 is most important. .
Can you give me the page number for that. I have the technical manual and the workshop manual
I definitely did not do that adjustment correctly.
My manual the pages are not the same as yours. See full procedure below. In step 6 ,the 2 connectors that are unplugged are identical so be sure to mark them so they don’t get mixed up when going back together.
My page #’s are different than yours but the angle sensor procedure should be in the last few pages of the “ELECTRICAL SYSTEM / Inspection and maintenance “
I appreciate that, I’ll be able to get back on the machine in a few days I will adjust that correctly and report back
Ok we’ve been back on the machine today and correctly adjusted the angle sensor. Machine still has a slow intermittent hydraulic issue. We have not had the machine long and we have been trying to figure out this running issue before did the standard maintenance stuff like new fluid and filters so other than knowing that there was hydraulic fluid in the machine we knew nothing. Since we still had an intermittent slow hydraulic issue after adjusting the angle sensor and the weather was nice we decided to drain the fluid and replace filters. When we took the lid off the tank to remove the big long filter it wasn’t in there and that valve and spring thing that sits between filter and lid were gone! Could that missing filter and valve and spring cause the issue we are having!?? Can anybody explain to me what the function of the valve does??
No , the missing filter, valve and spring would not create intermittent slow hydraulics. . The valve on top of the hydraulic filter is the filter releif valve . . I would suggest to check the EC and the PVC ground wires for good solid connections with the cab/ floor. If I remember most of the ground wires are all bolted in the area of the seat pedestal mount on the cab floor. I had a Deere 490E had some intermittent hydraulic performance issues and ultimately that’s what I found was the issue.
When you are doing the maintenance,Be sure to check the hydraulic pump suction screen is still in its proper place in the bottom of the hydraulic tank at the outlet flange.
With that filter not being in the system like it was the fluid didn’t get to be filtered and I believe that was what was causing the fluid to be so aerated. We thought the fluid just looked like it had some water in it but when you look at sight glass with a flash light shining across it you can see it’s full of tiny bubbles. So much so that we thought the fluid was milky but it was just that aerated. Wouldn’t that cause pump and all sensors to be erratic because those bubbles can compress under pressure? If so then I could see the computer and sensors chasing around trying to satisfy pressure and flow. I can’t think of why else the fluid could get aerated so bad. Keep posting advice it’s helping us tremendously with getting this thing going. It ran much better today after angle sensor was set correctly. Ram flawlessly until the fluid got aerated
The aerated hydraulic oil although not an ideal situation , I do not think it would be the cause of intermittent slow hydraulics. Since you discovered the hydraulic return filter was missing completely,maybe sooner than later check the condition of the hydraulic pump suction screen in the bottom of the hydraulic tank. Also , after operating you should be able to feel or hear a slight air pressure being released when removing the hydraulic tank filler cap ? The air pressure in the tank helps to force the hydraulic oil to the hydraulic pump.
Did you guys figure out the hydraulic issues? I have a ex120-2 and have sorted out a few issues. It now the hydraulics are getting hot 160°-170° after running 1hour. Lots of power and functions are fast. If I run in E mode it runs around 140°-150°. Curious what you figured out and any advice is welcome. Thanks