Hey y’all I bought a clapped 2016 299d2 xps high flow over the weekend and just starting to work through the issues. Had a bad alternator that was throwing a million overvoltage alarms. Had it rebuilt and all those are gone now. Had a lift linkage position sensor voltage alarm. Replaced bad fuse and that one’s gone now. I’m down to 2 yellow alarms. 2687-8 Right drive motor speed sensor #1 Abnormal frequency pulse width or period 2688-8 Right drive motor speed sensor #2 Abnormal frequency pulse width or period Also getting a red alarm when moving the machine: E695-3 “Unexpected Motor Speed Detection Disabled Drive speed is limited until fault is corrected” I’ve tried pulling the sensor and cleaning it and swapping the plugs on the sensors under the cab and it stayed as the right sensor. Anyone else have any ideas? Serial CAT0299DJFD201128
E695-3 “Unexpected Motor Speed Detection Disabled is a direct result of the speed sensor problems. Fix them and it should go away. See the attached procedures. I would suspect something in either the common power or the common ground for the RH speed sensors circuit which is two separate sensors in a common body.
Awesome thank you Nige! I will start going through the procedure when it cools off a little later.
Or the less likely possibility that a common fault is present in the signal wires from both sensors. There is an intermediate harness connector (CONN 7) between the RH speed sensor and the Machine ECM. It might be an idea to check that for dirt, condensation, or green crusties.
So I worked on it today and got 8v at the sensor plug. Was going to do step 2 on the diagnostic but read you have to drive the machine for codes to clear. So I tried swapping sensor plugs again and drove it. Got the left and right side sensor alarm now. If I switch back and drive it I only have the right side. Wondering why I’d have both still if sensor is bad. Wouldn’t I just have the left side if sensor is bad?
The Code for the second sensor was caused by you unplugging it. The machine has to be driven maybe 20 yards or so to clear Codes on the speed sensors. I would suggest that if you have established the 8v supply is good try switching the sensors side for side and see what that does for the Codes.
You mean like completely removing them and switching sides? I tried switching the plugs and yielded the results above.
That is exactly what I mean.
Were you measuring the voltage between Pins 1 and 2 of the 4-pin connector and did you have it connected or disconnected from the sensor.?
I can do that. I measured between the top two pins looking at the plug face with the latch on the top. Colors didn’t really match the diagnostic guide. Was two yellow wires. The other two were grey and purple. I was measuring it unplugged from the sensor.
This is actually quite important. A couple of posts above I posted the wiring for the LH side motor speed sensor. Below is the wiring for the RH side. I would suggest that you start looking for the numbers on the wires themselves because if someone has been in there messing around previously you may be chasing your tail testing wiring that is not connected the way it should be. The wire numbers repeat every 6" or so on the insulation on the outside of each wire. If you look at the back side of each 4-pin connector on the machine side of the wiring harness you will find the pin numbers moulded into the plastic housing. I would suggest that you make sure the connectors are wired correctly with each individual wire, identified by colour and number, in the correct location on the connector. This also applies to the wire positions in any jumper harness that might be on the machine. P769-Yellow and P770-White are common to both LH & RH sensor connectors because they are the 8v power and return wires. If you test for 8v between those two wires try it first with the connector unplugged then by backprobing with the sensor plugged in to be sure that the voltage reading remains the same. Only the signal wires will be different; 832-Brown & 833-Grey on the RH side, 834-Yellow & 835-Purple on the LH side.
Ok so I finally had time to look at it tonight and believe I may have found something. There definitely was a repair made at some point. I’ve attached a picture of the repair and the connector (ignore my toes.) I believe the repair was made incorrectly. Based on your RH side wiring diagram, white wire from ECM should be going to pin 2 on the connector but it’s going to either 1 or 4. Brown from ECM should be going to pin 4 but it’s going to pin 3. I’m going to unwrap and rewire the connector based on your diagram tomorrow, check voltage and see if it fixes anything.
I suspected that. It’s not unknown for the speed sensor wiring to get damaged in a machine such as yours. That’s why I went into all that detail above regarding the wiring. I would suggest that you do not use butt splices for your repairs as they will likely cause problems when condensation eventually gets into them, as it surely will. Personally I would solder the wire joints and use marine-grade adhesive heat shrink over them.
Just thinking a bit further about your issue. Irrespective of any potential incorrect wire connections those butt splices could well be a source of problems, especially in the sensor signal wires. Your two "-8" Codes specifically relate to "Abnormal Frequency, Pulse Width, or Period".
Yes I plan on soldering and using some marine grade heat shrink. Fingers crossed fixing the wiring fixes the issue. Hoping it didn’t fry the sensor getting power sent to the wrong places for who knows how long.
Good/bad news. Fixed the wiring but still had right alarm. Swapped plugs and now the left throws an alarm but right alarm goes away. Previously had both alarms after switching plugs. So good news is the plug is wired correctly but now problem moves downstream to either the jumper harness or sensor on right side. Plan on pulling the jumper harness to inspect it for shorts tomorrow. If harness checks out I’m guessing sensor is probably fried.
I would suggest to use something like a 5A fused test light when testing for continuity. Connect one end of the wire to batt+ via the test light and the other end of it to machine frame ground. Often a wire can show as good with a multimeter but that's only sending maybe 25 milliamps through it. The true test is whether or not it will pass significant current.
Pulled harness and couldn’t find any damage. I tested for continuity between wires and couldn’t find any so I took a chance and bought the speed sensor. $300 later (ouch) machine is fixed and has no more yellow codes. Ty for all the help Nige, you da man!
Look at it this way. You now know a lot more about your machine electronics than you did before you started.