289D Drive motor speed sensor faults 2685-8

I have a 289D, TAW05187, that has abnormal drive motor frequency faults for all 4 speed sensors (2685, 2686, 2687, 2688). It has the intermittent fault that only shows when moving the machine. I've gone through the service manual and all the wiring checks fine according to the troubleshooting guide. I initially started checking wiring at machine ecm and working toward the speed sensors themselves since it was all 4 sensors and I felt it was a common fault. 8V ref was reading about 7.95 at every point I tested it. All grounds I tested were good. I swapped in a spare speed sensor from a 279D that I had lying around with no changes to any readings. There is a small amount of hydraulic oil on the face of the sensor when I remove it. I know that could cause an incorrect reading on the sensor but the fault happens so quickly that I don't believe it's the source of my issues. I had a tilt cylinder fault 458-4 that went away when I replaced the sensor. I only dug into that because it used the same 8V reference. I've also got a 3700-3 inclinometer fault that has been around for quite awhile. We haven't looked into that one because the dealership said it won't affect anything other than the operation of the self leveling function of the machine and my 279D had had the same fault for about 6 years with no other side effects. Once I started looking into that I found that the inclinometer uses the same 8V ref. Could everything that uses that reference signal cause problems elsewhere in the circuit? I've googled "can an inclinometer fault 3700-3 cause 2685-8 speed sensor faults" twice and the AI said no the first time and yes the second so I'm reluctant to trust that. I have started looking into the 3700 and I think that I've got a ground issue on the inclinometer circuit as I get around 1000 ohms on step 2 of the 3700-3 troubleshooting tree. Most of the threads I find on this either don't resolve or come down to a sensor or wiring. Not came to that point as of yet. Just really looking for an idea on where to go from here. Should I track down the inclinometer problem in case it's the root of my issues or am I headed in the wrong direction. I have the service manual and diagrams for the machine as well as ET. Any advice would be appreciated. Thank you.

Just went through the 3700-3 troubleshooting again. Seems as though I had a bad ground when checking things late yesterday. Went through from start to finish and it's telling me my inclinometer is faulty. As in my original post, with that fault active, could this be driving all of my speed faults? I've also found that the 8V ref powers the roller switch on the right joystick which we use with our grappling bucket almost exclusively. If there was an issue there, would I have faults associated w/the joystick? Thanks again

flipz34 said: I have the service manual and diagrams for the machine as well as ET. Click to expand... OEM service manual or aftermarket.? If you haven’t already done so can you download a Product Status Report and post it up. Can you give a bit more back story regarding the speed sensor Codes. Did they all appear at once or what.? Were they hard faults right from the get go or have they been coming and going for a while before setting permanently.? EDIT: Regarding the 3700-3 inclinometer fault - If the wiring as far as the sensor is good then the Code should change to a 3700-4 if you unplug the connector closest to the sensor. From previous experience on the forum there is history of the wiring harness for that sensor getting rubbed through, so it may pay you to inspect it closely.

Nige said: OEM service manual or aftermarket.? If you haven’t already done so can you download a Product Status Report and post it up. Can you give a bit more back story regarding the speed sensor Codes. Did they all appear at once or what.? Were they hard faults right from the get go or have they been coming and going for a while before setting permanently.? Click to expand... I'll have to figure out how to post up the report, never ran that one before. It's the OEM manual. 268X codes all appeared at same hour. That was over 100 hrs ago. This has been a backup machine as I worked on some emissions/engine issues. Emissions faults had highest priority so I never noticed that the speed sensor faults were an causing an audible alarm at the same time

flipz34 said: I'll have to figure out how to post up the report, never ran that one before. Click to expand... See this YT video. The only thing you have to be careful to save it in Adobe Pdf format as opposed to the default .xml format (mentioned round about the 6:00 mark) otherwise the person reading it has to have ET on their computer in order be able to see the report.

Here is the report. Without the inclinometer connected, I have the 3700-3 active. Connecting a jumper to ground per step 5 of the troubleshooting, the active code switches to 3700-4 telling me the sensor has failed

Another suggestion. I’m personally not keen on the resistance tests to check wiring integrity in the troubleshooting procedures for the speed sensors. A wire can be hanging on by a thread and still register continuity if you only measure resistance. I would suggest that you check wiring using a fused 3-5A test light. Unplug the wiring at both the sensor end and also at the 70-pin plug on the ECM. Jumper one end of a specific wire to machine frame ground then apply batt+ via the test light to the other end. If the wire being tested will pass that amperage then I reckon you can call it good.

It could be that the speed sensor circuits are more sensitive to bad 8v supply/return signals than the thumbwheel. For what it's worth, disconnect the inclinometer sensor harness up the top, just before it starts to run down the load frame, where it branches off from the main machine harness.

I was finally able to get back out to the shop and build a load test light using a spare cab work light I had lying around. All wiring to speed sensors light up as do the three wires to the inclinometer. Light seems just as bright through machine harness as it does connected directly to the battery. I did find the the harness was plugged in backwards (LH sensor connected to RH harness) as I was hooking everything up. Corrected that but I'm not sure if that could cause the issue I'm having. I'll get everything hooked back up and test tomorrow.

That fact that the sensors were crossed up means that the problem is on the RH sensor not the LH and the Code should change from 2685-8 to 2687-8 when wired correctly. Can you confirm that happened.

I've had 2685, 2686, 2687 and 2688 from the beginning, so all 4 speed sensors are faulted. I disconnected the inclinometer harness at the firewall so everything running down that arm is out of the system. I've got all 4 speed sensor faults and all the associated faults that come as a result of disconnecting that entire harness. I'm stumped at this point. Could I have an ecm problem? I know it's not likely according to the service manual but I know it happens. My 279D has a problem with the ecm output for the bucket coupler actuator. Are there any other sensors on that 8v reference line that I'm missing? Could I have a problem with a joystick? The roller on the right uses 8v reference and we use a grappling bucket almost exclusively so that roller sees a lot of use.

flipz34 said: Are there any other sensors on that 8v reference line that I'm missing? Could I have a problem with a joystick? Click to expand... The following sensors are powered via the 8V supply from the ECM. 2 x speed sensor assemblies. Lift cylinder pressure sensor Tilt cylinder pressure sensor Inclinometer RH joystick thumb roller switch. The fact that you don't have a CID0041 FMI04 Code would appear to indicate that the 8v supply is good. I know that you tested powers and grounds for the speed sensors but did you load test the four signal wires between the sensors and the ECM.?

I did. I used one of the cab flood lights I had lying around. Regular bulb, not LED. The light was same brightness on signal wires as when I connected the light straight to battery.

Would I be able to use the machine ECM from my 279d (GTL00859) for troubleshooting my 289d? The 289 has a newer ECM but the parts diagram calls for the same ECM part number for both machines. I imagine that there could be some issues with the software on the 279d being a little older but would I be able to confirm or eliminate the ECM as the reason for my speed sensor faults?

flipz34 said: Would I be able to use the machine ECM from my 279d (GTL00859) for troubleshooting my 289d? The 289 has a newer ECM but the parts diagram calls for the same ECM part number for both machines. I imagine that there could be some issues with the software on the 279d being a little older but would I be able to confirm or eliminate the ECM as the reason for my speed sensor faults? Click to expand... I think you should be good. The ECM on the older machine updates to the same 464-2924 Part Number as fitted to the newer machine. Also the flash file software Part Numbers are in the same "chain" so although the newest software may have more bells and whistles the older software should still do the job for the purpose of a test. See this article. The 568-2606 software mentioned in it updates to 573-6365. Basically it illustrates that the GTL and TAW machines should be running the same software.

So I was able to swap the machine ECMs. Problem went away but came back within about 10 seconds. Put original ECM back and started buttoning everything back up so we could get it out of the way while we figured next steps. Decided to change the gear oil in the drives while it was down. When I was rotating the drive motors to line up the drain ports the right side was stationary while the left was moving. Ran it this way multiple times to make sure I wasn't moving joystick off center and it was the same every time. My understanding is that they would move in unison. Am I wrong here? I was wondering if the left drive was bypassing fluid and not driving until pressure rose high enough. I put a hose on the case drain port of the drive motor and both sides are putting out about 2-3 quarts in 10 seconds under load. I believe that from what I read on here and I think Texas Final Drive's website that a healthy drive motor would barely wet the bottom of the bucket. Am I looking at 2 drive motors on the way out? Is my original problem related or is this coincidental? I feel like I am chasing my tail here. Thanks again for all the help I've gotten here.

flipz34 said: I put a hose on the case drain port of the drive motor and both sides are putting out about 2-3 quarts in 10 seconds under load. Click to expand... Are you sure it was the case drain port and not one of the others.? A drive motor in good condition should put out a steady stream of oil about the diameter of a pencil from the case drain port when it is stalled. You can stall it by putting something like a towbar pin in the drive sprocket. flipz34 said: When I was rotating the drive motors to line up the drain ports the right side was stationary while the left was moving. Ran it this way multiple times to make sure I wasn't moving joystick off center and it was the same every time. My understanding is that they would move in unison. Am I wrong here? Click to expand... They should, but only if the hystat pump swash plate control solenoids are correctly calibrated. There are 4 of them for LH and RH, FWD and REV respectively. A calibration of those solenoids might be a good first step.

Yes it was the case drain line and the stream was about pencil sized. I went to do the calibration this morning for the left joystick. With machine off and all other parameters matching ET requirements (eng speed, park brake, hyd locked out), I get the 695-3 fault immediately when I touch the joystick. If the engine is off and the machine isn't moving, how can I have an unexpected drive motor speed? Could it be something with the joystick base? Because the ECM doesn't recognize the machine is stopped, I get a 101A and 101B error code (FWD and REV on joystick) and the calibration fails.

flipz34 said: I get the 695-3 fault immediately when I touch the joystick. Click to expand... That is to be expected. If there are no valid speed sensor signals the four "Unexpected Motor Speed" events (E568, E569, E570, & E570) cannot work and therefore E695 (Unexpected Motor Speed Detection is Disabled ) pops up. Have you ever removed both LH & RH sensor assemblies for inspection & cleaning.? Do you have a known good speed sensor to use for a test.? Maybe from the same machine as the one that the ECM came from.

I have swapped in a good speed sensor we had in the shop. Both sensors have been removed and there was a slight amount of oil on them. No more than I've ever seen on any others when they were removed. It just got my attention that the engine was not running and the fault appeared when the joystick got bumped