Working on a friends machine and not quite sure how bad it’s looking. Started with a no start/no cab power situation. I found no power at the key so I ran a jumper wire from the batteries around to the key, everything in the cab now works and the machine starts with the key. I’m assuming broken/chewed wire. Second issue is an issue with faulty shutoff solenoid. Have to hold it open manually to get the engine to run. I tested for power with the key on at the 3 pin connector for shutoff, no power on any pin. I tested for ground and have a ground on all three pins. Should I automatically assume broken wires or could it be a fuse/diode? If so where and how do I test the diodes? Third issue being throttle. Machine had no throttle so they ran it with throttle pulled manually. Tested for power at plug for throttle knob, had 5 Volts on one. Tested resistance on knob and had OHM reading from .6-4.4OHM as we turned the knob. When trying to use the throttle with machine running it won’t go above idle and the stepper motor or actuator makes a high pitched noise until the key is off. When the key is on you can’t really move the motor manually but when the key is off it moves freely. Any help is appreciated. Thank you.
-
Thank you for visiting HeavyEquipmentForums.com! Our objective is to provide industry professionals a place to gather to exchange questions, answers and ideas. We welcome you to register using the "Register" icon at the top of the page. We'd appreciate any help you can offer in spreading the word of our new site. The more members that join, the bigger resource for all to enjoy. Thank you!
Komatsu PC270-LC6 No Key Power, No Throttle, No Shutoff
- Thread starter NNYDairy
- Start date
John C.
Senior Member
The machine a couple of fusible links in the battery compartment as well and a battery isolator switch that works off the key switch. Here is a video that shows how the disconnect works.
The should also be a fuse panel in the cab. They usually have a black cover that can be pulled off to reveal the fuse panel. It's been a long time since I have stuck my head in a Dash 6 machine so I'm not entirely sure on the fuse panel. Don't move the throttle lever when there is no power to the key switch. The stepper motor on the throttle control can turn into a generator and actually harm the computer. If the alarm works, you will usually hear it squeal when you move that arm with the key off. Let us know what you find.
The should also be a fuse panel in the cab. They usually have a black cover that can be pulled off to reveal the fuse panel. It's been a long time since I have stuck my head in a Dash 6 machine so I'm not entirely sure on the fuse panel. Don't move the throttle lever when there is no power to the key switch. The stepper motor on the throttle control can turn into a generator and actually harm the computer. If the alarm works, you will usually hear it squeal when you move that arm with the key off. Let us know what you find.
Yeah I believe that’s labeled as a “battery relay” in this machine. I have power coming off that but not making it to the key switch which is what led me to believe the wire is broke somewhere between the two. The real trouble I’m having is with the throttle and fuel shut off. Throttle worked until they lost power from key switch therefore losing power to everything in the cab. So they disconnected the throttle linkage and ran it manually. Got power back to the key/cab today tried throttle and it won’t work.
John C.
Senior Member
Throttle is a function of the computer. Did you check both fusible links. One supplies the power to the key switch while the other feeds everything else. I think there are also 14 or more diodes in the system, most located in the right rear corner of the cab. They are all taped to the wiring harnesses. Do you know how to check the diagnostics on the monitor panel? You probably don't have power there either but I'm just checking.
John C.
Senior Member
Here is a video that shows how to get into the monitor panel diagnostics.
Diodes are easy to check. You just remove it from the harness and use an ohm meter. Touch the probes to the connectors one and then reverse them. A good diode will read through one way but not the other. A bad diode with read through both ways or neither way.
Diodes are easy to check. You just remove it from the harness and use an ohm meter. Touch the probes to the connectors one and then reverse them. A good diode will read through one way but not the other. A bad diode with read through both ways or neither way.
So I think I have the throttle issue narrowed down to the stepper motor being shorted out due to manually running it. I tested the plugs and have power and grounds on both plugs. But as for the fuel shutoff solenoid I am a little hung up. I tested for power with the key on, machine not running. I had no power on any of the three pins in the connector for the solenoid. I tested for the harness side of that connector for ground as well and have a ground on each pin. Should I be seeing ground on each pin? Also I understand there’s supposed to be power to open the solenoid while cranking, then power to keep it open. Does the power to keep it open show up once the machine is actually running or should it be there now with the key on? Thanks
John C.
Senior Member
I'm guessing that your machine has a Cummins clone engine in it. The Komatsu engines shut off on the throttle linkage and didn't have a shut down solenoid. The should be codes in the diagnostics that will tell you the problems what the problems are.