I know this is a common thread on the forum, but I am having some of the same Issues with both left and right drive motor speed sensor codes. I have used the procedure to check the wiring. Continuity is good on all wires through both harnesses. I replaced the hydraulic filter, and the gear oil in both drive motors. There was no sign of metalic in the oil. I removed both sensors and cleaned. (no sign of debris on sensors). They clear after tracking for a ways, but come back in any time the machine is put under load, such as climbing a steep incline, or pushing and scooping dirt. Before replacing both sensors, is there any other things that could be causing this.
Depending on exactly what codes are logging, could be a hundred reasons. What codes are you getting? Any performance/low power concerns? Is there a delay on one track when shifting from low speed to high speed? Is is stuck in high speed? Does it even have high speed? A s/n would also help.
Thanks for the reply. Serial # is JJST01153 It is 2 speed but it does not seem to be stuck in high. There is no delay in either track when engaging high gear. Codes are Unexpected motor speed detection disabled. E695-3 2685-8 2686-8 2687-8. I have seen a low 8v power code at one point but i don’t recall the code. Alternator shows to be charging fine.
Ok. Next question, are all three codes becoming active all at the same time? I would expect 2688-8 to be amongst those codes too, is it? I'd be very keen to know what the 8v power supply and return is doing when they become active. You can spoon into both of them at the ECM. They should run at about 7.8 volts most of the time. Go below 7.8 you'll get codes. Wiring or ECM for me.
Yes, all four are coming in at the same time. Where is the ECM actually? Do you know a part number for the harness from ECM to sensors? I tried tracing the harness up from where the speed sensor jumper ties in. I can track the machine around all day and never get a code, but as soon as I put it under load I get them.
Do you have a schematic? There will be at least three harness sections between ECM and drive motor speed sensors. I wouldn't throw parts at it just yet. Find out what your 8v sensor supply/return is doing first.
Thanks Chrisso I do not have a schematic. Where can I find one, and an actual photo of the ECM location under the cab?
@Nige may help out with that. I reckon there's only one ECM bolted to the underside of the cab. That'll be your machine ECM, the one that you want to test the 8v circuit on. Once you have the schematic it'll all make sense.
You rang.? To the OP - check your messages. TBH I think it is unlikely that both sensor assemblies (each one is 2 separate sensors in a common body) have all failed. Much more likely it's wiring and because the supply & ground for all 4 sensors is common that's where I personally would start looking first. Attached the troubleshooting procedure for and FMI 08 fault for all four sensors
Update. I replaced jumper from harness to speed sensor. Ran the machine for an hour with no more Issues. Thanks guys for the help.