Hitachi zx225uslc throttle not working

[Martin Canuel]

I have a 2006 zx 225 uslc zeroswing
No communication with drzx pda with machine.
Machine won't respond to throttle dial.
Machine won't turn off with key. Must use manual shut off
I've replaced the throttle motor with a new one and didn't fix it, replaced key/ignition cylinder.
On the 3 pins ec sensor while running at idle I read 4.5v 1.7v and ground. Regardless of throttle position those readings don't change. Also tested the 4 pins on the motor side and
pin 1 is (. 2 to 1.4) fluctuating
pin 2 is (. 2v)
pin 3 is (. 5v)
4 is ground.
Any insight would be amazing I'm pulling my hair out. I've done a relearn probably 8 times doesn't do a thing.
Motor doesn't even make sound now when starting. Randomly will work fine one day then next no response.
Ive tested the across the ec sensor coils as per the tsb about these ec motors as well and 1-2 reads 1.07 and the 2-3 reads 1.18
Bad ecm??
We had a thumb and catwalks welded onto the machine recently, battery disconnect switch was off the whole time. This is also a intermittent issue now was sometimes it will work on startup then no throttle response.

 

[mg2361]

Welcome to HEF Martin! F4, F8, F10 and F18 fuses good? If those "F" numbers are incorrect they would be the Main Controller and Engine controller fuses. If the fuses are good then the most likely issue is short in one of the 5V reference wires to one of the sensors. Those controllers are designed to shut down the throttle if a short is detected in 5V reference circuit.

 

[LACHAU]

Refer to troubleshooting below. Also check the Control Dial Value.
Sometime machine can work===>the faulty may be loosen of any electricity connector??!!
Hope that MC (Main Controller) is not faulty!!

 

[LACHAU]

You can also check machine status and fault codes without Dr.ZX PDA as follow.

 

[Martin Canuel]

Welcome to HEF Martin! F4, F8, F10 and F18 fuses good? If those "F" numbers are incorrect they would be the Main Controller and Engine controller fuses. If the fuses are good then the most likely issue is short in one of the 5V reference wires to one of the sensors. Those controllers are designed to shut down the throttle if a short is detected in 5V reference circuit.

Thank you!!, Glad to get some input finally! Iam concearned as well about my drzx not communicating, i can do a data download on the one plug but on the mcx i get no communication.. to test that 4 pin plug what should i be reading on them>
I did check the fuses behind the seat yes, reading wise to test those circuits what should i be reading at each one of those fuses?

 

[Martin Canuel]

You can also check machine status and fault codes without Dr.ZX PDA as follow.

View attachment 205409

View attachment 205408

View attachment 205410

Thank you so much for this infomation, ill go through this today and report back with some findings!
Also in regards to "Also check the Control Dial Value" iam assuming you are referring to the actual dial below the screen for the throttle, and your meaning talking a resistance or voltage measurement on those wires that go to the dial?

 

[Martin Canuel]

You can also check machine status and fault codes without Dr.ZX PDA as follow.

View attachment 205409

View attachment 205408

View attachment 205410

In regards to looking at values on the screen NO LUCK
I turn off machine hold set button, turn on, let go of set button press display and after pressing the 4th time for display (engine actual speed value) i get 6 dashes (- - - - - ) and from there the screen is frozen doesnt matter what i press i cant see anything else other than those dashes if i turn off and on again with key then it restarts.

 

[Martin Canuel]

Refer to troubleshooting below. Also check the Control Dial Value.
Sometime machine can work===>the faulty may be loosen of any electricity connector??!!
Hope that MC (Main Controller) is not faulty!!

View attachment 205405


View attachment 205403

View attachment 205404

Ive gone though these steps and results as follows
Disconnect sw panel and resistance between panel side connector terminals 2 and 4 is supposed to be 5+-0.5 my readings were 160k ohm, 157k ohm and 131k ohms did 3 readings to be sure spec is supposed to be 5+-.5 k ohm so book says if not within spec change dial control..

also the voltage on terminal 3 does not change when plugged in regardless of dial position my reading was .8v and did not change. book says faulty engine dial...... however the chart you sent says a faulty dial would not effect the key off issue iam having that is where im a tad confused..

NOW the interesting part i did the ec sensor testing flow chart as well
resistance between terminals 1 and 3 on ec sensor side is 2.07 checked my old servo motor it was 2.3, spec is 2.0+- 0.4 spec says all is good there
Next, ec sensor voltage on harness eng connectors between 1 and 3 with key on i get 5.18v spec is 5+-0.5v so good there
Now iam unable to watch the voltage change due to the fact i dont have this st7129 harness, is this harness anything fancy or is it just a way to tap into these wires, why cant i probe them while its connected and watch the readings??

from there it says to check harness between terminal 18 and ec sensor for short or breakage...
being unable to test with that harness i did the other steps, i checked voltage between ec sensor harness and end connector on terminal 1 and read 5.18v spec is 5+-0.5v, bok says broken harness between mc and ec sensor terminal 3

During this whole process while i was in the cab i reconnected the dial harness and i heard the servo motor move, i played with the dial and could hear it moving back and forth. i fired up machine and idled up and down with dial.. after about 15 seconds no response from dial.

Leaning towards dial control panel? not being able to access the onboard diag via the set button is kind of worrying me as well maybe i was doing something wrong??

 

[LACHAU]

In regards to looking at values on the screen NO LUCK
I turn off machine hold set button, turn on, let go of set button press display and after pressing the 4th time for display (engine actual speed value) i get 6 dashes (- - - - - ) and from there the screen is frozen doesnt matter what i press i cant see anything else other than those dashes if i turn off and on again with key then it restarts.

As I know that you have Dr.ZX tool. Please use service mode for setting monitor display as follow.

 

[Martin Canuel]

Unfortunately No communication with drzx pda with machine, i get a no cumminication error check power or communication cable error message.

 

[LACHAU]

Unfortunately No communication with drzx pda with machine, i get a no cumminication error check power or communication cable error message.

Attached file is Electric Circuit diagram.

 

[Martin Canuel]

So judging from what ive discovered so far, am i safe to call the throttle dial ? or leaning towards the ecm??

 

[LACHAU]

...Next, ec sensor voltage on harness eng connectors between 1 and 3 with key on i get 5.18v spec is 5+-0.5v so good there
Now iam unable to watch the voltage change due to the fact i dont have this st7129 harness, is this harness anything fancy or is it just a way to tap into these wires, why cant i probe them while its connected and watch the readings??

Yes, it's just a way to tap into these wires.

 

[LACHAU]

By the way. It's very simple to check stepping motor by using ST 7125.
It's same follow video.

 

[Martin Canuel]

Wow you are so open and helpful this is amazing!!!! ok will test that tomorrow and post back with results. Thank you Thank you

 

[LACHAU]

So judging from what ive discovered so far, am i safe to call the throttle dial ? or leaning towards the ecm??

My dear,
Throttle Dial 's just a 5 k.Ohm "POTENTIOMETER".....very, very cheap.

 

[Martin Canuel]

So first do the test on the servo motor by tapping in to those plugs, if not then calling the dial??
Doesnt the no communication with the dr zx worry you? also the fact that the dial is only responsible for one of the 3 problems in that flow chart and isnt related to the other 2 leads me to believe there is another issue no?

 

[LACHAU]

So first do the test on the servo motor by tapping in to those plugs, if not then calling the dial??
Doesnt the no communication with the dr zx worry you? also the fact that the dial is only responsible for one of the 3 problems in that flow chart and isnt related to the other 2 leads me to believe there is another issue no?

as i already told you: Hope that MC (Main Controller) is not faulty!!
I don't know whether you can repair MC or not!!

 

[Martin Canuel]

Worst case new mc is 500 ish online just money they make it every day. Just dont like throwing parts and not getting results

 

[mg2361]

i dont have this st7129 harness

You can backprobe the connector to check voltages.

Iam concearned as well about my drzx not communicating, i can do a data download on the one plug but on the mcx i get no communication.. to test that 4 pin plug what should i be reading on them

Unfortunately nothing published that I know of that will have that information. However is there not a 6 pin plug to plug into? I think that is the one you want. Lachau, can you confirm?