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
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Hitachi ex120-2 intermittent slow hydraulics for all functions.
- Thread starter Newberryi
- Start date
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
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
Diesel Dave
Senior Member
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).
https://www.heavyequipmentforums.co...u-load-the-hydraulics-on-hitachi-ex200.31811/ .
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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.
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).
https://www.heavyequipmentforums.co...u-load-the-hydraulics-on-hitachi-ex200.31811/ .
.
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.
Diesel Dave
Senior Member
The EX120-2 manual KM105E03 is out there .
If you have trouble finding one, it’s available at the Deere Bookstore.
www.johndeeretechinfo.com
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?
Diesel Dave
Senior Member
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.
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?
Diesel Dave
Senior Member
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??
Diesel Dave
Senior Member
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.
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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
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??
Diesel Dave
Senior Member
Good call @ Shopguy.
Per manual , Fault code 27 indicates that the sensing signal (input
voltage of the sensor) is higher than 4.75V .