Hello all, got another typical fun drive motor problem on this Cat 299D2. SN- FD200669. Currently throwing a 2686-8 error as soon as machine is keyed on. Its showing 16k+ rpm on left drive motor speed even when not moving. And when you operate the machine, it also immediately throws the E695-3. It started doing it on and off randomly a couple weeks ago and is now a constant error. Machine still drives okay. I have checked resistance and load tested the harness all the way to the machine ECM. The 8v circuit is fine also, and I also switched the connectors for the left and right motor speed sensors, the problem stays for the left side and does not follow to the right. Also replaced the left speed sensor. I plan on trying the calibrations when I get back to it just in case but wondering if there were any other ideas as its really looking like an ecm issue. Thanks
On the face of it does look like an ECM problem but that would be very unusual. The wiring is usually the culprit. I suppose the best test would be to put a known good ECM on your machine and see what happens. Before shelling out for a new ECM it would be worthwhile repeating all the wiring tests. Do you have an electrical schematic.? How did you load test the harness if you don’t mind me asking.?
I do have the factory wiring diagram. I have a couple car light bulb setups and power probe to load test, so I can run some amp load in the circuit. I tested each section of the harness multiple times. Speed sensor jumper harness, chassis harness, and chassis harness up to ecm connector. I checked the 8v supply, return, and both sensor wires all the way to the ecm. I also back probed the 8v side while everything was connected and key on, no issues there. I also had no codes associated with the 8v side and the right side functions fine, it gets its 8v from the same harness. Really last thing I can think of to completely rule out the wiring is to run an overlay harness right out of the ecm connector, right to the speed sensor. Resistance was also around 0.3-0.4 ohm all the way to the ecm. I dont abe access to a known good ecm either unfortunately.
If you have a schematic then try swapping the signal wires from the LH #1 & #2 speed sensors at the ECM plug and see what happens to the fault. If it changes from 2686-8 to 2685-8 then you have your answer.
Will do, thanks.
Actually you could play wiring bingo in a couple of ways. What I suggested above requires Deutsch connector de-pinning tools but you could also switch the #1 & #2 signal wires at the 4-pin Deutsch connector located next to the sensor itself. TBH I suggest that you do both, but do one first and observe the results then put the wiring back to original at that location and swap the same two wires at the other location.
Will do, will be back over there next week. Thanks Nige for the help as always