Need help cracking the code on a Hitachi 120-2 with pump control issues

[mclean]

Ive been dealing with a slow hitachi 120 for about a year now. The problem seems to be pump sensor related. Ive had the machines pump solenoids plugged in backward for the past year. This made the machine quick enough and powerful enough to move and do simple jobs. If the solenoids were plugged in properly the machine has a relief valve loudly hissing constantly, and stalls when functions are pushed, especially swinging.

Today I put a new position sensor on the pump. Now when the solenoids are plugged in backwards the machine is almost non responsive, but does move, just very slowly.. Same hissing and related when plugged in the correct way.

Im trying to figure out what this may point to?

I believe this shows the solenoids are working, as they seem to be reacting when they're played with.

The fuse for the computer isnt blown.

Would the dp sensor be the next move?

 

[mclean]

Another possibly related problem is the track speed or the dig/ lift functions dont seem to work? Always assumed it was due to the pumps low flow but maybe part of the issue?

 

[mclean]

I have uploaded a video of the two computers blinking at each other.. http://youtu.be/wakTjol47S4

Im not sure if they're acting normal, or if they're blinking me a code?

Any help with this would be much appreciated.

 

[rgl726]

that's a normal status blinking not fault codes.

you need to short the dr zx. socket to get the fault codes.

 

[mclean]

How do I short the dr zx socket?

 

[rgl726]

send me your email ad.

 

[mclean]

Thank you rgl, you have been extremely helpful!

Now, ive reset the codes, and am getting 28, and 31

Is there a cheat sheet to see what all these codes mean?

 

[mclean]

I've been meaning to update this thread for any poor souls in the future digging to find information to help remedy their "Hitachi -2 blues".

After counseling from RGL (thank you) I was able to get the computer to flash the codes at me. (Jumper wire in both right hand quadrants of the dr zx port) There were quite a few.. Luckily a quick reset of the codes (Start with jumper in socket, shut off for 10 sec, restart remove for 1+ sec then replace) cut the list down to 2, which was much more approachable.

Code 28, and 31

28 is a fault with the P sensor (at this point I had discovered the pressure sensor's housing was broken and suspected it was involved with this -2 nonsense.)
31 is a over voltage in the sensing circuit, T or A sensor unplugged or internal fault.

With this information, I went on Ebay and bought all the control sensors from China.

After I got all the new sensors, I installed 1 by 1, hoping to discover which was my issue.

Started with the angle sensor, then did the pressure, then the dp, then the tach. NO CHANGE!

I noticed the solenoids weren't clicking like they usually did, so I took the angle sensor back off and it smelled like hot electronics. I replaced with the old one. Solenoids started clicking and the machine is back in working shape.

My -2 Blues were caused by possibly the pressure sensor or the dp sensor. Leaning towards pressure because of the broken housing, but the connections were still good on the inside, so who knows? Im just glad machine is working again..

Im fairly sure the Chinese sensors are a gamble. out of the 4 i bought 1 was bad. Maybe 1 for 4? I was warned by others that they aren't to be trusted.. But for the price! Now we'll see how long they last.

Hope this helps someone, I noticed during my searches, that there was a lot of machines with these sensor problems.. The hardest decision will be buying from China, or spend 10x at a dealer.

 

[mclean]

By the way, any one replacing the tach sensor should be warned that there is a good supply of oil behind the sensor. So have a plug or the new sensor ready to put back in the hole..

 

[holeworx]

hi.I have a EX120-2. i have similar faults. I am working through basic maintenance items. my next is the Battery charge light flickers.so alternator rebuild. anyway.when cold only it will stall out.I have overhauled the cooling system and have a thermostat in it.the sensor under the main pump was leaking oil.I have replaced that. I have cleaned all wiring plugs and re greased then with dilemic grease.when cold it makes the strange hydraulic pump noise like its under load when idling.off and on.it used to stall out 10 - 20 times .when warm she will work all day.with all my maintenance bits ,it has got better .I have even done the fuel system and thimble gauzzes in the fuel lines.yeasterday it only stalled x2 .what is the location of the computer ? my next check mite be the codes ? all the rev controls appear to work correctly. even the snail and rabbit

 

[joelx777]

I've been meaning to update this thread for any poor souls in the future digging to find information to help remedy their "Hitachi -2 blues".

After counseling from RGL (thank you) I was able to get the computer to flash the codes at me. (Jumper wire in both right hand quadrants of the dr zx port) There were quite a few.. Luckily a quick reset of the codes (Start with jumper in socket, shut off for 10 sec, restart remove for 1+ sec then replace) cut the list down to 2, which was much more approachable.

Code 28, and 31

28 is a fault with the P sensor (at this point I had discovered the pressure sensor's housing was broken and suspected it was involved with this -2 nonsense.)
31 is a over voltage in the sensing circuit, T or A sensor unplugged or internal fault.

With this information, I went on Ebay and bought all the control sensors from China.

After I got all the new sensors, I installed 1 by 1, hoping to discover which was my issue.

Started with the angle sensor, then did the pressure, then the dp, then the tach. NO CHANGE!

I noticed the solenoids weren't clicking like they usually did, so I took the angle sensor back off and it smelled like hot electronics. I replaced with the old one. Solenoids started clicking and the machine is back in working shape.

My -2 Blues were caused by possibly the pressure sensor or the dp sensor. Leaning towards pressure because of the broken housing, but the connections were still good on the inside, so who knows? Im just glad machine is working again..

Im fairly sure the Chinese sensors are a gamble. out of the 4 i bought 1 was bad. Maybe 1 for 4? I was warned by others that they aren't to be trusted.. But for the price! Now we'll see how long they last.

Hope this helps someone, I noticed during my searches, that there was a lot of machines with these sensor problems.. The hardest decision will be buying from China, or spend 10x at a dealer.


View attachment 126194

Please explain the reset process a bit more clearly, it did not work on my machine.

 

[holeworx]

I've just been talking with my mate this morning about bringing life back into my ol 120-2 .I have Chinese solenoids on the shelf for her .thanks for the updates

 

[anton_baydak]

I have uploaded a video of the two computers blinking at each other..

Im not sure if they're acting normal, or if they're blinking me a code?

Any help with this would be much appreciated.

How did you decode the codes. My blinks 8 times on repeat