Can anyone tell me where the left drive motor speed sensor is located on a cat 259d???
Right on the bottom of the drive motor. The wiring harnes connector should be easy enough to spot.
Dear Nige thanks a bunch for your answer. I hate to sound so elementary but is there 2 drive motors and if so then where is this drive motor located. As you can tell I'm no diesel mechanic but i learn pretty fast. I'm just trying to get acclimated to this recently purchased machine i got. Once again thanks for all who will chime in and help me out on this one
Hi Bill, yes two drive motors, one on each undercarriage. Both have speed sensors that need to read correctly. First thing first... raise the cab and check all plugs and wiring, especially those that branch off to both undercarriages under the cab. Next, get the machine up on blocks and remove the bolts/plates on your axles that stop your undercarriages falling off. If the bushes aren't seized you'll be able to slide the whole undercarriage out a few inches for better access. 2685-8 is "Unexpected Motor Speed Detection Control" on the LHS motor so start with the LHS. May need to remove a few hoses to get to the allen head bolt for the sensor, maybe not. Remove sensor, look for any metallic debris. If you cant find anything wipe it clean and swap sensor with the one on the RHS undercarriage. Three things could happen: 1) Nothing, 2685-8 keeps reoccurring, problem is still in your LHS speed sensor wiring. 2) Fault changes to 2687-8 which is "Unexpected Motor Speed Detection Control" for the RHS, which means the sensor is bad. 3) Fault mysteriously goes away. Could've been tiny piece of metallic debris on the sensor from general wear, or could've been a bad connection somewhere in a plug.
Does this help.?
Chrisso I was able to get the machine on blocks as instructed and surprisingly i saw what appears to be that plug. And it is just hanging. It appears to be attached to the drive motor but ithe other end is not attached to anything. I'll send a picture to see if this is definitely the sensor. Of course it is dirty but it's the best picture i could get. I may be able to clean the area a little better to get a better picture. My question is: what is the other end supposed to be attached to. I assumed it should be attached to a wire coming from the machine but i don't see one unless I'm overlooking it. I also have the cab up as you instructed. Is it possible to send me somewhat of a diagram of what that plug looks like or comes from? Thanks a bunch for your time and patience
That'll run alongside the hydraulic hoses and through the machine frame connecting under the cab. Easiest way for you I think is to look at the RHS. That connector (receptacle) and the bit it connects to (plug) are called deutsch connectors. Looking at those photos they will both need to be replaced before reconnecting. If you post your s/n and ask nicely Nige will probably send you a schematic.
I tried to look at the other side but i couldn't see it. I'll try to look again today at the RHS. And i will most definitely post my S=N and ask Nige to send a schematic. Information is helpful that you've provided thus far
Another question. Is this a fault that has appeared suddenly or has it been there for a while now.? You haven't bought this machine recently with the fault present on it by any chance have you.? The reason I ask is that my first thought when you said the harness/sensor connector was hanging was that your photo would show torn wiring (possibly not unusual if a tree root or similar has been jammed in there). The fact is that it doesn't, it shows what appears to be an unplugged connector. Based on photo that the "other end" (aka the male half of the connector) should be around somewhere not too far away. Looking at the other side of the machine ought to give you the best clue. Again this comes back to Serial Number. There are 8 different models of 259D (also plus potentially different sub-models within that 8) and it would be of major benefit to know which one of them you have, not least to help in posting an illustration of what the wiring that connects from the machine chassis to the speed sensor ought to look like.
That is exactly what happened. I bought it a week ago with this issue already just trying to rectify it and the loud beeping. I just recovered my serial number. It is as follows: CAT0259DPFTL07252. I will try and see what the RHS looks and runs to
A lot of head scratching could have been avoided if you'd volunteered that information in the first place........... Attached is the parts diagram of the platform wiring but I am not sure if it will help you much. You might be better served investigating the other side of the machine and see how that is connected. I'm wondering whether this machine has had wiring ripped of at some time before you bought it and the previous owner simply couldn't be bothered to fix it correctly. If that is in fact the case the $64k question is what state the wiring is in at whatever point it was damaged. It might not have been repaired because it can't be repaired if you get my drift.
Yes that isa really good question. I hipe thats not the case. I'll start with replacing the speed sensor. However i was able to get the T40 allen screw out but couldn't manage to get the actual sspeed sensor out. Is there any magic to it? I assumed it would fall out once igot the screw out. I even tooka small hammer and tried to jar it a loose but to no avail. It looks like the original one but i still wouldn't think it would be this hard to come out.
Have you tried replacing the connectors and plugging it back in? Not sure why you're removing the sensor since you found the harness unplugged.
Because i sent pictures of the sensor and a senior member suggested that by looking at the end of the sensor it may need replacing. However i blowed it out and cleaned it and was going to try and see if that did the trick. Problem is i can't seem to find the end that connects to the sensor. I'm referencing the end that comes from the tractor. I just looked under the machine and saw the end of the sensor unplugged but didn't see what to plug it to. I'll look again today if i get off work in time. But what I'm faced with is that i saw a dangling wire which happens to be the sensor. Can't see where it goes. ANY SUGGESTIONS???
Only what was suggested before to look at the other side of the machine. The connections should be similar if not identical.
Ok I'll try that tomorrow. Its tough to see that sensor from the bottom for some odd reason
This is the only wire coming from the machine that i see dangling. It does however reach to the speed sensor on the machine but does not fit. I've sent photos and as you can see, the grey plug coming from the machine does say DEUTSCH as you suggested and the speed sensor that's bluish/green. They look like they should connect but the plugs dont match. My question is: is there possibly another piece that attaches to make these two fit? And also I've tried everything within my power to get to and view the other side but my view is highly obstricted by the hydraulic hoses and i can't see the RHS at all. Otherwise i would access it and use it for reference. So are these the two plugs that i need. Thanks again for all of your troubleshooting and expertise
Your first photo shows what appear to be the TWO halves of a 4-pin Deustch connector (see photo below) plugged together. If you look closely at it the end closest to where your photo was taken it should unpug from the other half by pressing the plastic lever shown arrowed on the LH half of the connector. This ought to leave a connector to which the one on your sensor (your 2nd photo) will plug straight into. To confirm that it is the correct wiring you're looking at, please check the wire colours/numbers that come into the back side of the connector and that they correspond with the terminal pin numbers shown below. they should be P769 Yellow, P770 White, 834 Yellow, & 835 Purple.
This appears to be very helpful information. I'll try to get off work early today and see if i can find an end that looks like the one you sent me a picture of
Working only from your first photo which doesn't show the inside end too well I still think that's what you'll find. Another thought. If you do find that it works as I described above be sure to carefully dry the inside of both halves of the connector before plugging it all together. It may be a trick of the photo but your 2nd one appears to show water inside the end of the connector. There is an orange silicone rubber seal between the two halves of the connector and any condensation trapped inside could cause all sorts of long-term problems.
You're correct, i did get a little water in there while trying to clean it for the picture. I'll be sure to blow it out really good and make sure it's dry before i connect them. I also tried to send better pictures of the inside of the connectors
Based on that photo I'm 99% certain that what you are looking at on the machine end is a complete connector that will need one half of it removing before you can hook your speed sensor connector to it.
That makes sense. I'll definitely try it today when i get home from work
Nige your 99% prediction was 100% correct. There was a half connector on the wire coming from the machine. I separated it and took the half connector off and it fitted right in there. However the code was still there. Do i need to reset that code or does it automatically reset? And if so then how do i reset the code? Once again Nige thanks for your expertise, patience, and information.
Turning the battery isolator off for a few minutes and back on again usually does it. If you don’t have one disconnect your battery... Let us know if that works.
Doesn’t the machine also have to move a few revolutions of the travel motor to produce a kosher signal from the sensor.? Try doing both and see if the Code disappears.
Good point Nige.
Nige you and Chrisso are genius. You guys instructed me to the fix to my problem( a complete novice with no real formal training) by process of elimination. I got it up on blocks by lifting the rear with my backhoe and used the bucket of the skid steer to elevate the front. Then i raised the cab(very easily by instructions from you tube). That way i was able to access that speed sensor from under the cab and the bottom of the machine. I took the old speed sensor out with the allen screw, changed it, unhooked the battery for 5 minutes, and whatta ya know? Boom... PROBLEM SOLVED. Again thanks for you patience nd expertise
You got it sorted Bill that's the main thing. You're welcome.
I hate to resurrect an old thread, but I have the problem with the left drive motor speed sensor. I've inspected things and found a connector that was only part way inserted, and so I cleaned and then properly connected it, and was hoping that was the problem. But, when I run the machine I still get the warning message and the annoying beeping on the control panel. This made me think the problem is not solved. But, in reading the last replies in this thread, is it possible that I need to do the battery-disconnect reset procedure to stop the message and beeping on the panel? In other words does the message and beeping continue even though the problem has been repaired? Thank you, Garret
I think the disconnecting the battery bit was a bit of misinformation from me. If the problem is fixed and the speed sensors are reading correctly, the codes clear (go from active to logged) usually as you're driving it out of the shed.
Ok. That means it's not repaired. I figured that was the case. I'll dig deeper and see if I can find where the sensor is on the motor. I spent an hour looking at it today, and I cannot find anything that looks like the sensor, or it's wiring, that's in the photos at the motor end. What's under the cab looks right, but then the wiring goes into a very thick hose that looks like a hydraulic hose, and then to the motor, with a steel fitting, or so it appears. So another question: Is it necessary to remove the whole track and carriage assembly from the torsion springs in order to get to the sensor? Or, as I read in this thread, can you get to it by only lifting the cab and then working from underneath? I'm hoping to get this machine going this weekend. Any help is appreciated. Thanks!
It depends how wide the tracks are. With narrow tracks they're fairly accessible with machine on the ground. Wide tracks (where you can't get your arm in between the machine frame and the track) you have two options: slide the undercarriage out a few inches or get to it from underneath. I find it easier in either case to raise the machine. But that's up to you. The speed sensor wiring is hidden in a hose that looks just like the other hydraulic hoses, except it runs to a bulkhead fitting (with wires coming out of the other side of the bulkhead fitting), not to the drive motor like the rest of them.
Very helpful. Thank you. My machine has narrow tracks and I can get my arms in there from above or underneath. There were a lot or roots, dirt and debris embedded on the back of the motor. It took me a while to clear it out. I'm hoping that's an indication that it could be a wiring issue. I could see where the hose seems to go to a bulkhead fitting, but it looked like it was going into the motor. Probably just my view was not good. I'll get back out there and look closer. For history, I bought this machine as a used machine from the local Cat dealer a couple of months ago. I have not used it much since delivery and it's been nothing but trouble. I had thought they would have gone through it, cleaned, checked and lubed it, but no, not at all, not one bit. Garret