Hi everyone, I’m looking for some help with my 2016 John Deere 650K dozer (about 1,800 hours). I’m having an issue with the transmission speed control that I haven’t been able to figure out. When I press and hold the button to increase speed, the speed increases like normal. However, as soon as I release the button, it immediately drops right back down to 1.0 where it started. It won’t hold the higher speed setting at all. The rest of the machine seems to operate normally. There are no warning lights or codes showing up. The machine hasn’t had any recent work done, so nothing has been disturbed or replaced recently. Any advice on what to check next would be greatly appreciated. Thanks in advance.
Try going into the monitor service menu ( push and hold the menu button for 5-10 seconds and it should say ''service menu''. You can scroll around the menus with the next and select buttons until it says''live values'' and push select. Use the next and select buttons to look at the engine speed values and you can scroll around until you find the trans speed control live value and see if the feedback changes when you push the up and down buttons on the speed in grip sensor. The ECU sends the engine speed to the TCU over the ''CAN'' and the best I can remember the speed control defaults to 1.0 if the TCU isn't getting an engine speed signal. See if any codes are active in the monitor as well. You'll be ok navigating around in the monitor as long as you don't push anything and hold it ( except to get into the service menu ). You can also compare the speed control sensor live values to the calibrated values and see if they're the same. The trans speed setting should be 1.6 when you crank up. See if it goes down to 1.0 before you release the parking brake too.
I just tried to find live values and was unsuccessful and the machine starts out at 1.0 not 1.6 if that tells us anything? I did learn i was wrong about stored codes and there is a tcu 581.03 if you hit the down button quickly after holding the up to come up from 1.0
What I can find about the code is ''speed button short to power''. Try unhooking the speed in grip sensor ( you can remove the 4 screws holding the control quadrant and pull the whole assembly out the top side ). Disconnect the speed control sensor and see if the code changes to a high resistance code. One one the wires going to the speed buttons could be shorted inside the handle.
It sounds like the speed control sensor is stuck in the down position or the wires are rubbed or shorted in the handle. The part # for the sensor nis AT376578 and is $467.57 and the grip assembly with the sensor is part # AT376577 and is $525.19. The complete grip may be your best option since it's already assembled and the little screws and plastic parts can be tough to work with. I googled the part #'s and didn't see any for sale used or on Ebay but you may be able to find it from a salvage source. I think if you just disconnect the speed control sensor on the machine it should run at 1.6.
I believe that is exactly the spot were having a problem, do you know what parameters I should see if I used an oscilloscope to check the outputs of that switch? Im betting its pwm because it looks like it is a micro processor
It gets a 5volt source voltage from the TCU. The three way connector has the 5 volt supply wire is terminal A, the return path wire is terminal C and the feedback wire to the TCU is terminal B. If you search around in the monitor the speed control live voltage feedback is in the ''live values'' menu. with neither up or down pushed the voltage should be 2.5 volts or so, the feedback with the up or down button pushed should be .75-1.1 volts ( approximately ) and 2,9-3.9 volts ( approximately ). I'll try to find the acceptable voltages in TM but if you see the voltages going up and down from the 2.5 or so the speed control sensor is working correctly but if the voltage stays much higher or lower than 2.5 the speed control sensor will probably need replacing.
Sounds like you're definitely on the right track with the handle harness/switch assembly. Before spending $500 on a new grip, try pulling the boot up and inspecting the wiring right where it flexes going into the handle. 9 times out of 10 on these Deere K-series hydrostatic dozers, the wiring inside the joystick neck gets pinched or chafed from constant movement, which will pull that 5V signal wire down or short it out and throw the TCU 581.03 code. If you find a rubbed wire, soldering and heat-shrinking it might fix your issue without having to replace the whole unit.