Good morning ladies and gents, need some help with a mini here Serial# 1736...So operator was complaining of a throttle issue. When in full throttle and operating, occasionally the unit would idle all the way down. He would then have to turn the dial down and then back up to restore to full throttle. Ok seems simple enough, you've essentially got 2 pieces that could be defective. Well we couldnt down the machine so i decided to replace the potentiometer first. Since it was cheapest. Same issue. Ok great, guess its the controller. Replaced. No ive got no throttle and an error code. E05. Went through the service code menu and it gives me "328" Well that doesn't exist in my manual...and it is an active code. So i go through the trouble shooting and the potentiometer voltage is off. 1.7 at idle and .3 at max. Ohms out normal. So manual says, faulty harness..replace...ooookkk which harness is faulty and why all of a sudden? Plugged old controller back in and the code goes away but still no throttle function. I replaced both components with genuine parts. Not to say they cant be faulty from the factory. But if i supply voltage through the controller harness directly the motor runs. Side note, This machine blew the bucket cylinder line and sprayed hydro everywhere including inside the cab. I didnt notice any oil infiltration into the wiring but figured id mention it. But thats what downed the machine and allowed me to replace the controller. Any help would be greatly appreciated.
Wouldn't there be a pressure switch on the pilot circuits, via resolvers, to close when pilot oil is sent to any function? That's what I would've looked at first. That's if it has auto throttle control.
It does have a deceleration switch for "auto idle" and it also wont let you idle up under a certain ambient temp until the coolant temp raises to a specified degree. But i dont believe it operates off of pilot switches. At least there is nothing noted in the diagrams or theory of operation. From what i can tell its all electrical operating off of inputs from the ECU/TCU.
Hi, As you mentioned "But if i supply voltage through the controller harness directly the motor runs." According to this statement it seems that there is a problem in your wiring harness. If that has happened it should be indicated from the controller as a faulty code. And your new controller has indicated that correctly according to your explanation and your old controller did not indicated that. It seems your old controller it self also has some problem if i am correct. If you can bypass the controller harness and run the motor as you mentioned, try to work with that arrangement and see whether your old controller works fine. I think still there will be some issues with that, things like suddenly idling down as you mentioned. Because i guess your old controller has some problems. If that happens then put your new controller and do some works to see whether your throttle motor runs fine with out any problem. If motor runs correctly that means your new controller is good and there is some problem in the wiring. If you have a wiring diagram, then do a continuity test, ground short test & B+ short test for wires that goes to the motor from the controller to determine the state of the wires.
Ive done continuity and all. All checks out good. For whatever reason my voltage isnt correct. Im getting just over 2 volts to the control box. Supposed to be 5 or greater. Made a call to the dealer service manager. Hopefully he can shed some light especially with this mystery code. Also the manual is awful when it comes to testing procedures and diagrams. tells you to check ohms, check voltage.."bad harness" "Bad controller" No pin outs or anything. Guess i shouldnt be too surprised. Dealerships are parts hangers anymore anyway. The manual just attests to that.
The usual issues with throttle controls on Komatsu excavators are almost alway wiring related. Check the harness connectors at the governor motor, there are two plugs. I haven't been into a 138 in years but as I recall the wires loop around some hangers under the muffler and the insulation cooks till hard and then breaks up. The copper then shorts against the hangers. I assume the potentiometer you are speaking of is the throttle dial. The ohms reading doesn't make a lot of difference and won't tell you wether it's bad or not. The computer only works with the amount of change. When you turn the dial the computer figures that as max and stops. When you turn the dial more the computer just makes that new setting the max and stops. This goes on that way until the lever on the engine governor hits that stop. The increased amperage draw tells the computer the lever won't go up anymore and sets that as the new max. It does this every time the engine is shut down. I don't know which computer and monitor panel you have in your machine. Can you take a photo and post it. Asking a service manager any technical questions is usually a waste of time. They are only paper pushers and don't know much of anything technical about the machines they are dealing with.
Good morning and thank you. I snapped some pics for you. The manager was actually somewhat helpful with my mystery codes and I have come to grips that it must be a short. I just don’t know where. My “governor” is not in the engine bay but rather under the cab. My connections all look fine. Tried swapping the relays and all. No change. So my next step is to start pulling off wire loom to try and find a rubber or broken wire.
I've looked at the photos and that is a can of worms. I think I would at this point start looking for ground points that wires in the harness hook up to. Komatsu usually puts their cabs on rubber isolator pads and then provides a separate ground wire from the cab to the machine frame. I've found those to be problems in the past on older machines. Those wires can be found inside the cabs sometimes and underneath sometimes at the back of the cabs. There was a very helpful and knowledgable gentleman from southeast Asia that was more knowledgable than me on these newer machines that might have some input for you.
Awesome, Thanks. I put that machine on the back burner here for a min and ill check that out once i get to it. All the wires are incased in wire loom so i found it pretty unlikely to have had a rubbed wire. Possible ground issue sounds more plausible.
Hey Lanchau! Get in here!
The fuel control motor is a DC motor. Worm gearbox to keep itself in position when the motor has no power. Accel relay turn ON to increase engine speed (Decel relay must be OFF). Deceleration relay turn ON to decrease engine speed (Accel relay must be OFF). The controller receives the signal from the dial control to increase or decrease the speed, the feedback potentiometer to let the controller know that motor is at the correct position.
Where did you measure Voltage?? What's number of connector pin, CN-CR1 , CN-CR2 or CN-CR3 ??
I realized i never posted a reply/solution to this. Computer ended up being fried, not putting out correct reference voltage. Replaced computer and was back up and running. Thanks for all the help.