Hitachi ZX35u-3 Limp mode *flashing SYS light*

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corksil
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Hitachi ZX35u-3 Limp mode *flashing SYS light*

Post #1 by corksil » Wed Nov 08, 2017 7:58 pm

Hey guys, simple question.

2011 hitachi zx35u-3 mini-excavator (4tons). Was running fine, and then the throttle dial/switch became unresponsive. Machine would start right up with the key, but it would idle around half-throttle and turning the engine-speed-dial had no affect.

Took apart the right ignition switch area and found that the wires for the rotary throttle-control switch had chafed and probably shorted out. I found a test procedure which seemingly confirmed that the switch itself had failed.

100 bucks later I installed a new switch, two other tiny chafed wires, and repaired/reconnected everything.

Nothing has changed --- the machine still starts right up with the key but instantly the engine speed jumps and hangs at half-throttle. Turning the rotary throttle switch (looks like a volume knob, right next to the ignition switch) has no difference on engine speed.

There's also a flashing "SYS" red light on the instrument cluster. I was told that the machine is in limp mode, and that there is a way to reset it, and clear the fault code now that it has been repaired.

Anyone? Thanks!


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Re: Hitachi ZX35u-3 Limp mode *flashing SYS light*

Post #2 by Jeremy Rowland » Wed Nov 08, 2017 10:01 pm

Hi TC and welcome to CMN :wave: to be totally blunt you would need to speak to a Hitachi skilled engineer who had access to their software and who could plug a laptop into your machine and clear the code; unfortunately the manufacturers of many types of machines from cars to trucks to just about anything are making them computer reliant to prevent ordinary folks from fixing them.
The only thing I would suggest and you may have already done this is to disconnect the machines battery and leave it disconnected for a while to see if that resets itself; unless somebody on here has actually got round a similar problem and can help you I can't think of anything else, good luck anyway please let us know how you get on. :thumbup:

Jeremy


Topic author
corksil
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Re: Hitachi ZX35u-3 Limp mode *flashing SYS light*

Post #3 by corksil » Thu Nov 09, 2017 6:40 pm

Thanks for the reply, Jeremy.

The local service tech is willing to bring out a computer to plug into the hitachi and read/reset the code. His price is 150/hr and he charges from the moment that he leaves the shop, which is about an hour and a half from my house. That is to say -- it's going to cost me about 500 to have that code "read" or reset.

I've already tried disconnecting the battery. One person that I talked to said that the light should clear itself if all the mechanical problems are fixed. The service manual diagnostic tree points to the "engine controller unit" as the next faulty component. The person I spoke with also said that the engine controller units hardly ever fail so it's highly unlikely that it's the problem.

After typing this out and thinking more about it -- maybe there is still something mechanically wrong with the machine. I figure that disconnecting the battery would clear the code and reset the computer -- yet if there is still a fault somewhere, the code would indeed come right back and illuminate the light.

I've also been running the machine with a manual throttle control. Seeing as "limp mode" causes the machine to run at half throttle, I disconnected the throttle actuator and have been using a cable tie to secure the throttle at whatever speed is required for the current task. I have put about 20 hours on the machine this way, and haven't had any problems yet.


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