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Dan
Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 4878
Experience:  17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
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I have a 2002 Komatsu D31PX with the hydrostatic

Customer Question

I have a 2002 Komatsu D31PX with the hydrostatic transmission. Dozer pulls fine but he 1,2,3 speed indicator will not light up on the dash and the dozer will not shift up out of first speed. Is there a sensor, fuse, relay etc I can check or is it more serious?
Submitted: 1 year ago.
Category: Construction and Road Equipment
Expert:  Dan replied 1 year ago.

Hi my name is***** will be glad to try to help. First using a test light test all your fuses with the IGN switch on for power on both sides of the fuse. Any fuse with power on only one side is faulty. If all fuses are good and the wiring harness looks good to the display panel, try swapping relays one at a time with a known good one for test purposes. If the fuses and relays check good and the harness checks good then the problem is likely more serious with a potential ECU or controller failure and the dealer diagnostic software will be needed to check to see if it can communicate with the ECU for further troubleshooting for a possible failed ECU. Let me know if you need more help

Customer: replied 1 year ago.
Are there any other fuses or relays other than the ones located on the right hand side of the machine in the compartment under the blade control joystick?
Expert:  Dan replied 1 year ago.

Whats your serial number?

Customer: replied 1 year ago.
50101
Customer: replied 1 year ago.
Model D31PX-21
Expert:  Dan replied 1 year ago.

Yes there are some inline fuses and relays in the harness. Click these links for the parts diagrams to help.

http://komatsupartsbook.com/#?k=!0!2!1211!30!33

http://komatsupartsbook.com/#?k=!0!2!1211!70!86

http://komatsupartsbook.com/#?k=!0!2!1211!70!84

Customer: replied 1 year ago.
No fuse or relay problems, we had already checked all of them but we did recheck the entire harness with no issues being found.
We took the cover off of the speed selector on the left hand joystick control lever. I am not getting power to the pushbutton speed selector. Any ideas there?
Expert:  Dan replied 1 year ago.

Thanks for the update. Pull the hydraulic return filter and inspect it internally for fine metal/debris as well as the pilot control filter/charge filter for the same that would indicate an internal failure occurring in the hydrostatic drive pumps or motors. You can use the links I posted to access the rest of the parts book. Let me know the results

Expert:  Dan replied 1 year ago.

Hi, Did you get this resolved?

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