I have read many of the post concerning the problem I have on my 259D S/NDTFTL14393. When I move forward I get the following warning. E695-3. Unexpected motor speed detection disabled. Followed by 2685-8 left drive motor speed sensor 1 abnormal frequency pulse width or period. I have removed the sensor and inspected the wires. The wires appeared to be ok. I cked Continuity from plug under the cab to the plug at the speed sensor. Everything checks good. I replaced the sensor while it was already removed. ( no debris on old sensor) still the same code. I checked the plug under the cab and compared the voltage and resistance on both the left and right sensor. They both read exactly the same. There is voltage on 2 of the 4 wires. One wire is showing 8v and the other wire is showing 3.5v. Not sure where to go from here. Any help would be appreciated. When I pull up info on display in the cab it shows the rpm on the left drive motor at 16704.0 rpm and 0.0 rpm when machine is not moving.
E695-3 is a consequence of 2685-8. The electronics need both speed sensors working in order to detect which way the machine is moving (FWD or REV). With only one sensor on one side working the ECM can only detect speed of travel. Try doing this troubleshooting procedure. Post back with your results.
I have completed the testing on the left side speed sensor. Everything checks within specs. I’m down to the last step which is possible ECM bad. I know this would be very unlikely but possible. Any advice as to the next step. Thx
Did you remove the sensor and clean the nose end of it.?
Yes Sir. The original sensor was clean when I removed it. I purchase another sensor and installed it. I removed it again today and was clean. The new sensor is not a oem. I followed the trouble tree exactly and everything checks Good. Exactly 8v at the sensor with a good ground. The 2 signal wires ohm out at 2ohms back to the ecm plug. I checked to make sure no short to any of the other pins at ecm from the 2 signal wires.
OK, it seems as though you have covered the procedure pretty thoroughly. Now you are with the machine and I am not but IIRC there is something like a jumper harness for the 4 wires for the sensor on one side of the machine (can't remember which side off hand) where the sensor on the other side connects direct to the machine harness. Question: Is there any way that you can change the wiring temporarily so that the signal from the LH speed sensor is sent to the ECM via the wires that should carry the signal for the RH sensor and vice versa.?
There are 2 separate 4 plug connectors under the cab. It appears that both go back into the main harness. I don’t see anything like a jumper. I did early on switch the plugs (left side connector to the right side wheel sensor and vise versa) When I started it up and moved it gave me a code of 569-2. Unexpected left motor reverse speed detected. I switched it back and began the diagnostic that you suggested
Right. It appears as though some wire switching is going to be required. First you are going to need a few Deutsch connector unpinning tools. I say a few because they are only plastic and can break quite easily if not treated with care. See this link. Other sources are avaiable but these are the genuine article. The size you need is for 16-20 SWG wires. Deutsch 0411-310-1605 Removal Tool Shop Deutsch 0411-310-1605 Removal Tool at DeutschConnector.com. www.deutschconnector.com The signal wire for the LH speed sensor #1 that creates the 2685-8 Diagnostic Code is wire #835 colour Purple. The signal wire for the RH speed sensor #2 is wire #832 Brown. Go to ECM and unplug connector J2. Check the pins on the ECM and the sockets in Conn J2 very carefully for corrosion or damage. You will find wires 832 & 835 in adjacent Pins 37 and 38 of CONN J2. The idea is to use the unpinning tool to remove those two wires from the connector, swap them over, and reinstall. See this YT Video from 21:10 onwards that shows the use of the tool. The key is don't use a lot of force. If the wire/socket assembly doesn't won't to come out, slide the tool back out and rotate it by 90 degrees then insert it and try again. If as a result of the swap your current 2685-8 Diagnostic Code becomes a 2688-8 then you have a wiring issue despite the troubleshooting procedure indicating that this was not the case. If the Diagnostic Code remains as 2685-8 it is confirmed the problem is in the ECM provided that there is no obvious damage in the ECM Pins or Conn J2 sockets.
Great idea. I will be trying this soon and will be letting you know what I find. Thanks for the time you’ve spent on this.
I forgot to mention that when using the unpinning tool it is a good idea to push the wire into the connector as far as it will go before inserting the tool over the wire. This will probably not be much, maybe only a millimetre or so, but what it will do is take the weight off the two plastic "teeth" that retain the socket in the connector thus allowing the tool to open them up and for the wire/socket assembly to be pulled back out of the connector. The large-size connectors like ECM CONN J2 do not have removable wedges like the smaller (up to 12-pin) Deutsch DT connectors do. Instead at the bottom of each hole there are these teeth that click into place over a ridge on the socket once it is pushed fully into position to prevent it from coming out. This is maybe a better VIDEO explaining how to do it.
This may be completely irrelevant, but I don't know if I would trust the aftermarket sensor. I have seen many times in the automotive world where aftermarket sensors simply do not function correctly. Everything fits right, looks right, but the PCM won't read it . . .
Thanks Nige. I agree with not trusting the aftermarket parts. I’ve not ruled out that as a possibility yet. The original sensor and the aftermarket are both showing same symptoms. I did order it from a reputable off road parts supplier and not just Amazon.
there is a big BUT here…… These speed sensors are actually two sensors moulded into a common body. It seems strange the the output of the #1 sensor was bad both with the OEM original sensor and also with the aftermarket will-fit, yet the output of the #2 sensor was good with both. That to me seems to rule out a sensor issue.
Great info. Really appreciate the time.
The system only needs one of the two sensors on either side of the machine to function in order to measure speed, but it needs both of them working in order to determine direction of travel. Why.? The two sensors are located at specific points in the nose end of the sensor assembly. As the gear in the drive motor passes the two sensors it does it as slightly different times. If #1 sensor sends a signal to the ECM a hair ahead of the signal from #2 sensor then the ECM knows that the machine is travelling forward. If #2 signals ahead of #1 then the machine is going in reverse. Simples......
Just to be clear. My code is saying that sensor #1 is abnormal. If both sensors were abnormal then it would be giving a # 2 sensor abnormal as well?? With #1 being the only fault that is why your suggesting to switch just that wire at the ecm. (Speed sensor #1 circuit)
Yes indeed. The Component Identification Numbers for the four sensors are as follows:- LH #1 - 2685 LH #2 - 2686 RH #1 - 2687 RH #2 - 2688 Exactly. If the problem is a wiring or a sensor issue (long odds on LH #1 sensor being bad on two different sensor assemblies though) issue then swapping the LH #1 signal wire with the RH #2 signal wire should cause your current 2685-8 to change to a 2688-8.
Understand. Great info
Acksherley you could swap the original OEM sensor that was removed from the LH when you installed the aftermarket one and install it in the RH side. If it does not throw a 2687-8 (RH #1 sensor) Code then you have just proved that the sensor is good. The only doubt that remains at that point is over the wiring - back to the swapping wires test that I suggested a few posts earlier.
I’ve certainly got a lot of options to help me. I will certainly let you know how it goes.
Nige. I got back to diagnosing my Cat 259D left wheel speed sensor problem today. I did exactly what you suggested in switching the left side purple #835 with the right side #832 brown wire at the J2 ecm plug. After putting everything back together I ran the machine several hundred feet. The original code E569-2 was still active. After switching off the machine and cranking it back up 15 minutes later the warning now says Right side speed sensor 2688-8. When I go to the display that shows speed sensor rpm the left and right both show 16704.0 rpm at idle.
Let's not worry about all the rest of it right now. E569 will be there until ALL the four speed sensor signals are genuine. So the original Active 2685-8 Code has disappeared, to be replaced by an Active Code 2688-8, correct.? Which sensor is installed in the LH side right now, the OEM or the aftermarket.?
That is correct. The aftermarket sensor is installed on left side.
OK, so let's recap........... Two different sensor assemblies installed - same (original) Code - 2685-8. Signal from LH #1 sensor wire swapped at ECM end to Pin for RH #2 sensor. - Code moved from LH #1 to RH #2 sensor. You have a fault in the signal wire between the LH #1 sensorand the ECM, despite the fact that the troubleshooting procedure indicated continuity is OK. I have seen this before, and I take issue with Cat's testing procedure for continuity by measuring resistance. A multi-strand wire can literally be "hanging on by a thread" somewhere and give a resistance measurement that is in spec. However it will not pass significant current (for solenoid circuits) or a signal (for sensor circuits) without screwing up. You will need a fused 3A or 5A test light for this test. Unplug the connectors at both ECM J2 and the speed sensor so that you can test the machine wiring harness. On the 835-PU wire for the #1 speed sensor connect a jumper wire to machine frame ground at one end (doesn't matter which) and connect the test light supplied from battery+ at the other end. That will prove whether or not there is a defect in the 835-PU somewhere. Either the test light will glow consistently bright or it will glow for a second or so and then go out.
Sounds like a plan. It will be tomorrow before I get back on it. I’ll keep you posted. Thanks again for all your time and input
Before doing the test light procedure it might also pay you to de-pin the 835-PU wire in the 4-pin connector on the machine harness at the speed sensor end. Install the socket from wire 835-PU directly on to the #3 Pin of the speed sensor pigtail connector and do a "drag test". In other words see how tight the socket fits over the pin. Then maybe de-pin a different wire and repeat the same test. Is the socket for the 835-PU wire a looser fit on the Pins than the other three wires.? Just don't get the wire locations mixed up........ You could also check that the plastic finger that locks the socket in place is not damaged or broken. See this VIDEO at around the 1:29 mark. You can see them inside the connector before he installs the wedge that secures everything in place.
Update. I had a Deutsch connector kit so made me an overlay wire and ran it from the wheel speed connector all the way back to the J2 ecm connector. Overlaying the purple #835 wire. The original trouble code still exists. While doing this I have now picked up a left side speed sensor # 2 code as well. I removed the sensor to check again for debris on tip of sensor. It’s still clean. All connections and pins are clean and tight. The right side code cleared up after I had switched the wire earlier.
Is the code for the #2 sensor Active or Logged.? If it is Logged then in all probability it was caused when you pulled apart the connector at the speed sensor end. Did you try the "drag test" of the #835 wire socket on the speed sensor pigtail pins.?
Honestly I did not do the drag test. I will do that tomorrow. Not sure if the code is logged or active. I see both codes 1 and 2 on display when I run machine.
The difference between Logged and Active is that one is highlighted in yellow on the Advanced Display screen, the other in red IIRC.
Update. I did a little more on the Cat259D left wheel speed sensor problem today. I rechecked all connections by examining them really good and by removing the pin from connector and checking the drag. All this looked good. I then did an overlay wire on bothe the signal wires (yellow and purple) from speed sensor all the way back to the ecm. I moved the machine for a good distance and still have the red E695-3 warning as well as the yellow 2685-8 and the 2688-8 both scroll across the overhead display.
Correction 2686-8. Left side #2 not 2688-8
How far exactly did you move the machine.? Are the Codes on the display highlighted Yellow or Red.? OK, now my bet is on a problem with the common power supply or the common ECM ground to the LH side speed sensor assembly. The chance of two signal wires being bad at the same time is pretty remote, although possible I guess. Try disconnecting the battery overnight, then reconnect and move the machine at least 200 yards. See if the Codes go away then. E695 is a consequence, not a symptom. It won't go away until the 2685/2686 Codes are eliminated.
Will do. Thx
When you de-pinned the wires I hope you got them back in the correct locations in the connector.? Definitely need to know if the current Codes display Yellow or Red on the Advacned Display.
Yes sir. I’ve been extra careful making sure not to create any problems. This is what I’m seeing each time I move machine
Sorry I sent same pic twice
Update. After following some very good advice from Nige on diagnosing this speed sensor problem everything kept checking good. I was left with changing out the left and right side sensor. This is not a hard job but it is time consuming. After changing out sensors the problem is now on the right side. The left side has cleared. Seems to be a bad part. I’ve not replaced it yet but feel good about what I have found. Thanks again Nige for your time and feedback. It was greatly appreciated.
So in essence the aftermarket sensor that you purchased and originally installed on the LH side of the machine was bad right out of the box in regards to the same #1 sensor signal in exactly the same way as the OEM sensor originally installed in that location.? I wonder what the odds of that are.
Exactly. I would say the odds are pretty low. So low I didn’t want to believe it. However that’s how it goes sometimes. Still saved a lot of money by doing this myself and wouldn’t have been able to without your help. Thanks again
That's exactly why we test - multiple times if necessary.
Update. I emailed the company that I purchased the aftermarket sensor from. They were nice enough to refund my money. The next day they emailed me saying that they believe that the sensor I had was manufactured wrong. Not sure how they knew this but they were going to send me a new sensor free of charge. I decided to wait and try this replacement sensor instead of purchasing a OEM. Just got it today and installed it and all codes have cleared out and everything working as it should. Just wanted to say thanks again for the help with this.
Nice of them to man up and offer you a replacement. Even nicer that the replacement fixed the problem. You've been round and round in circles with this one simply caused by a faulty replacement part, and TBH there is always the possibility that a replacement OEM sensor could have had exactly the same issue. It didn't make diagnostics any easier, but at least you can sit back now with the knowledge that you know a heck of a lot more about your machine electronics than you did when you started...!!
You’re 100% correct. Thats the positive in all this. I’m just grateful that I had you as a resource and was willing to give of your time. I couldn’t have done it without you!