Hello, I’ve acquired a Komatsu PC200 and it seems the electronic throttle doesn’t work correctly. The 3 LED’s below the seat indicates an “electrical abnormality” as written in the operations manual. The throttle servo moves from idle to 50% as you rotate the speed knob from Min to 50%. As the knob goes above 50%, the throttle servo stays at 50%. I replaced the speed potentiometer after the recommendation of the dealer, but this yield no change in symptoms. When I grab the servo output lever and force it up or down, the servo still goes back to where the knob wants it . It seems like the engine management is limiting the speed, but selecting any of the “load” setting modes doesn’t give me more throttle. In lowest load setting, I should still be able to increase speed beyond 50% anyway, correct? Any thoughts on this matter would be most appreciative…
Because you have the diodes I am assuming you have a Dash 5 model machine. If the diodes are behind the seat and you have to open a mirror to view them, the machine is probably built for US consumption. If the diodes are below the seat and you view them from outside the cab, you have a gray market unit. The combination of lights is driven by the engine control computer. If all the lights are on you have a problem in the throttle control dial. Basically you are getting 50% throttle because the computer is not giving the right signal to the computer. If you have a combination of lights on and off, you need to state what that combination is. I have the old book for Dash 5 electronics and can help you. I have not seen many throttle dials go bad in all the time I worked on those units. Usually the problem is in the wiring harness. Have you done any recent electrical work on the machine. Generally I saw problems after someone added another fan, radio or lights. Oil on the harness can also give you fits. If it is the dial you can check it with an ohm meter. Let us know what you have or what you find.
Thanks for your reply , John. This unit is an grey market model, LED's below the seat and the keypad looks like the menu from the local Chinese restaurant. After the engine starts and things settle out, the LED's are lit in the following manner: #1 off, #2 Green on, #3 Red on. We've checked the display/controller push button panel for burned out components, bad connections, etc. but it all looks good. In picking the brain of a local mechanic, he mentioned there's a sequence of button pushes on the keypad to put the computer in "program" mode and to electrically stroke the throttle to zero and span the throttle. He couldn't remember the keystrokes to enable this mode, but said it was in the service manual. Does this sound familiar to you?
The book shows that as an "abnormality in governor potentiometer". Since you say you changed it there shouldn't be a problem there. You should check the wires coming off the governor motor. They go back to a couple of hangers that the couplers are stuck on. What I have seen a lot is the wires are looped around those hangers and rub on them hard. They wear through the insulation shorting out that particular circuit. The other problem is the muffler is right next to those wires cooking out the insualtion and the wire inside. I've seen plenty of those wires broken inside the insulation. The monitor panels on these machine do not have diagnostics. The displays on the each computer are what are used. You haven't mentioned the machine computer at all. Have you checked for codes on that one. As I recall there is a flip out mirror still for that one on the grays. It is further back from the LED group. If there is a code there it will be flashing. Normally it will show the mode and power setting, H1, S2, L3 and so on. Fault codes will be numbers 10,15,18 and so on. Generally when the engine computer has a problem, so does the machine control box. Good Luck!
The first place I would look as John mentioned is the harness rubbing on the hangers.
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Thanks for the all the info. I'll have a chance on Saturday to check out the wire harness, codes, etc. and I'll report back Kevin
Well, we found no smoking gun yesterday. We inspected the wire loom from throttle servo to cab and found everything in good shape. The one spot where the wire loom chafed was near the servo, but it only chafed thru the outer most layer of insulation and not the wires. There's a heat shield between the wires and the exhaust system, all the wires are in good shape in the vicinity. At the recommendation from a fellow mechanic who suspected the servo ( which retails for $1000), we took that out to the workbench and inspected it. It’s a reversible motor geared to the actuator arm and a 3 wire feedback pot. The gears are good, the pot. measures good through it’s travel, the motor operates fine. I think we can rule that out as the problem. One thing I don’t like is we couldn’t see any digital output from the computer’s display located behind the little door with the mirror. Is the power for the display separate from the computer or is it integral to it? We’re scheduled to have a major rainstorm for the next few days, so any further work will be pushed out till after the storm passes. It seems like the computer is limiting the throttle as opposed to a fault in the circuit to the throttle servo..... Kevin
The display is inside the computer. Take off the panel covering it and you will see two boxes. The three diodes are for the engine computer and the display is for the machine computer. I have seen issues in the main computer before but it is not common. I may be that you don't have the mirror opened in just the right spot. You can take it apart and look at the boards. I generally look for little burn spots. I have never been successful in trying to repair a board. There is also a bunch of diodes down the back side of the that console. If you follow the wiring harness from the computers you will see them connected. They will probably be blue on the ends but I have seen gray also. Good Luck!
We found some smoking guns today. We removed the covers around the machine computer , removed the 3 connectors from computer, noticed some moisture/corrosion at these connectors. We removed the computer and took it into the shop, opened it up and found wetness inside. The components on the board are sealed in clear silicon sealant. I’m in the process of cleaning and drying the board, can’t find any black spots, etc. so at this point I’m confident the board is OK. In looking at the actual circuit on the computer board, it appears that connector C3 is power to the board, C2 is sensors inputs, C1 is outputs to servo/solenoid valves. With the ignition on, I couldn’t find any incoming power to the computer on any of the 3 connectors. We found that spring clip for the machine controller fuse (#1 fuse) was damaged. This fuse is located at the front the row of fuses and takes the brunt of anything that could hit there…. the fuse cover being missing for awhile. We repaired the fuse holder, and I expected to see 24 volts on one of the connectors for the machine computer with the ignition on, but didn’t. FYI, with the machine computer removed, the engine computer shows #2 (green) LED while the engine is running, which is normal…no errors. John, could you reference the service schematics and tell me if the power for the machine computer comes from the #1 fuse, thru a relay, then to the computer via connector C3? Because, I’m not getting supply power to the computer, there must be a relay that pulls in to give it power. There are four relays in front of the engine computer that I don’t know what they do. If you could tell me what pin at what voltage on C3 is the incoming power, I can bench test this computer before I reinstall it. Monday, I'll see if anyone local has this service manual schematics. John, your manual wouldn't happen to be on .pdf format? Thanks, Kevin
Now you are starting to tax some of the old brain cells. Since there are no new ones I'll do the best I can with what I got left. First off my book covers 300s and 400s. Since Komatsu used essentially the same electronics package in all Dash Five machines from 120 on, we should be close enough to make this work. Pins 3 and 4 on C1 should be your power leads. They receive power from the key switch. The fuse for the key switch is number 9. That should be counting from the most forward fuse being number 1 and counting back. Fuse number 2 supplies power to the engine throttle computer. All this kind of makes sense for your problem because the speed sensor is run through the machine computer but your throttle control is run through the engine computer. No speed sensor signal and the engine throttle computer doesn't know what to do. Connector C2 on the computer runs all the relays and switches. Connector C3 on the computer receives signals from sensors. There is a jumper connector in the schematics in my book. In my book it is named M20 and should have four pins and two jumper wires out the back side. If your machine has this plug and set of jumpers I would check that for power. Most likely it is corroded. It would likely be somewhere around the key switch area. When the pins and sockets were corroded I used to take a jeweller's screwdriver and scrape them some to cleam them. All the pins and sockets can be pulled out of the harness connectors and replaced but I doubt you will ever find replacement ends. The dealer I worked at had the only electrical coupler kit I ever saw and the part number on the box no longer worked in the Komatsu system. I do have some simplified schematics I can scan and send to you but I've been gone all weekend and it's late. Drop me a PM and I can send them as an attachment through email.
Thanks for the schematics, John. After cleaning all the pins on C1, we found that the ground connection, pin #12 and #13 had lost the ground connection. I spent sometime looking for the ground connection on the chassis, but ended up splicing a new lead to the ground wire on C1. Everything works as it should! Thanks for your time and consideration! Back to making holes in the ground....
I'm glad to hear you got it fixed. Good Luck for the future.
:drinkupwell its about time......:drinkup
Hello, I am having the same problem with my Komatsu PC 150LC-6 excavator. I was woncering if you ever traced down your problem and if so, what did you do to repair it? Thanks Heath
No further repair was required. Somewhere there was a chassis ground wire that was corroded/broken. I provided a ground by adding a wire from the chassis to a common ground on the fuse panel. You'll need to have a schematic and a meter to troubleshoot. What is exactly your problem?
Thank you for the reply. The problem I am having is with the throttle or rpm varying. The error code E05 comes up on the screen. The service manual says its a governor system problem. It suggest to move the trottle linkage to one of the other holes in the bracket on the pump, or replace the linkage. I have done both. Sometimes it works fine and all functions work good. Then if I turn the machine off then restart it, the alarm sounds and the E05 code comes back on and rpm varies. ??
Presently i am working with my Pc210-5 excavator and having the same problem which bogging my mind. It frequently goes to limp mode registering codes #13, 14, 18, and 52. Does anyone knows what the codes meant? I just hope anyone could help me with these. Thank's and more power!!
I encountered the same problem before and it turn out to be a simple fuel issues only. Check your fuel filter and air cleaner and look also for any leakages in the fuel suction side.