Ex 120-2 problems.

[imgonnadigtochynaa]

I'm working on a 120-2 for a friend.
It was sent away to hitachi and a new pump installed for a constant full stroke issue.

I found the angle sensor installed wrong, then found it sending erroneous signals. I replaced with new and set it to 4.40 at full swash.

I found the pump control valves not getting 24v, the relay was not on, did not have a good ground. I then traced the harness to a bad connection on the floor behind the seat not sending ground to the relay and a portion of the pump control box, corrected and Relay started working.

While i was at it, i replaced the speed sensor, and the pressure sensor.

I've inspected every wire in the cab.

I checked the codes by jumping the Dr.zx connector, I get code 20 on the pump box, and code 4 on the engine box.
I removed and inspected all wires and connections between the boxes by continuity, aswell as opening up the boxes and thoroughly inspecting the pins and circuit board components visually.

I also now notice, the relay for the pump control now powers up for about ten seconds when the machine starts and then clicks off. Stopping power to the pump control valves. I beleive controlled by the pump box.

Could this be caused by the speed sensor or wiring? It is new but untested at the pvm. I have verified the sensor voltages are intact reaching the pump computer, but not tested the speed sensor as it's more of a pulse than anything.

The auto idle, and engine mode functions all work good.

Just stays at full stroke all the time. No matter what.
Unless you swap the 2 wire plugs to the pump control it goes to no swash (my understanding is proper)


Not sure where to look next beside blindly throwing pump control module and engine control module on.

 

[mg2361]

Welcome to HEF imgonnadig!

You got a tiger by the tail with this one.

When the engine is running, does the PVC light blink once a second?

PVC Code 20 - Signal from Engine Controller (EC) is not Transmitted to Pump and Valve Controller (PVC) (perform retry procedure B)

ECU Code 4 - Failure of Engine Controller (EC) (perform retry procedure A)

The retry procedures can only be performed with the diagnostic software, as far as I know.

I'll send you some restroom reading material. Check your messages.

 

[imgonnadigtochynaa]

Thanks, I received the reading material. My best bet might be to buy the diagnostic software at this point. Unless someone else has had similar issue.

In the manual I had a hard time understanding retrial a and b procedure.

Yes the lights blink normal 1 second intervals unless the ex is jumped.

 

[imgonnadigtochynaa]

I purchased the diagnostic software, and cable. Found the speed sense not registering on the pvc.
The speed control and auto idle work fine on the dashpad.
I tested the harness and read the pulse signal at the ec for the speed control and it is good.
Seems like it's the pvc not acknowledging the signal from the ec.

 

[KOBE STEEL]

I have never used the Dr EX or ZX tool and I don't have much experience on that model but try and see if you can get information on doing calibration checks on the pump position sensor and see if there is also a differential pressure sensor on the valve bank that may not be working correctly. I believe the pumps solenoids might be pwm controlled and the connectors were 2 pin male and female plugs so they couldn't be incorrectly connected.
Best of luck

 

[imgonnadigtochynaa]

Yes I can monitor every sensor, and have set the angle sensor. The only sensor not measuring is the rpm. Which it is receiving signal at the ec
My understanding is if the engine controller is working properly then it's most likely the pvc
I beleive the diagnostic only talks to the pvc on this model but I could be wrong

 

[mg2361]

I tested the harness and read the pulse signal at the ec for the speed control and it is good.

That is why your throttle still works. The engine rpm is then broadcasted to the PVC from the EC. There may be an issue with the communication wires between the EC and the PVC.

I believe the pumps solenoids might be pwm controlled and the connectors were 2 pin male and female plugs so they couldn't be incorrectly connected.

They are on/off solenoids, not PWM. Also, the connectors for the pump solenoids are identical, so they can be connected incorrectly.

 

[KOBE STEEL]

Thanks for the correction and sharing the knowledge mg, I always thought they may have been PWM controlled directly from the PVC.

 

[imgonnadigtochynaa]

So they aren't pwm? What relays operate th then?
I was under the impression they received 24v all the time and the pvc grounded at its discretion.

 

[mg2361]

I was under the impression they received 24v all the time and the pvc grounded at its discretion.

That is correct. They receive a constant 24 volts from the pump control relay, then the PVC controls the ground, but not with PWM, but just ON/OFF signals to open and close the solenoid valve. So there is not an infinite movement of the solenoid valve, it is either open or closed.