Machine is going into limp mode right at startup with warning alarm. Used to happen every now and then. Would turn off, back on and would clear up for a while. That will let the machine get back to work. Due to the responses on this website on other threads, I think I diagnosed it to the wheel speed sensors. Wire harness is good with good voltage (8v,5v). Just weird that I think both going out at the same time. I do have a couple questions on a few other codes. I will list all of them below 4336456 E875-2 E123 E570-2 E568-2 E569-2 2686-8 2688-8 2687-8 70-3 3700-13
This machine has 4 speed sensors. A pair on the RH side and a pair on the left. The sensors supply a PWM signal to the machine ECM. Each pair of sensors is mounted in a common body with a common power supply & ground. Each sensor has its own signal wire in the harness, so four wires total in each narness. 2687 & 2688 are the RH #1 & #2 speed sensors. The first suspect would be a fault in the common ground or power supply. 2686 is the LH #2 speed sensor. As there is no code for 2685 (LH #1 sensor) the first suspect would either be in the signal wire or a defective sensor. -8 indicates an abnormal signal from the sensor i- frequency, pulse width, or period. Post a S/N. with that detailed diagnostics and an electrical schematic can be lkocated. BTW E568, 569, & 570 all relate to issues with drive motor speed, so they will also be related to the sensor faults.
CAT0299DKNLC00311 So there is sensors on the drive motors themselves. I’ve checked those yellow wire voltages one at 8 and one at 5. So you’re saying there is other sensor under the cab somewhere
No. the speed sensors are mounted directly to the drive motors. The sensor is #1 in the illustration below. If you were measuring voltages with the sensor disconnected that's not the correct way to do it. You need spoons for your DMM and measure voltage into the back side of the connector with it still plugged to the sensor. The sensors are fed with stabilized 8v from the ECM. There is no 5v at that point.
So just want to double check this cause I’m kinda a dummy sometimes.. the white and yellow wire according to the manual should both produce 8 volts
Not exactly. Yellow wire is 8v sensor Supply, White is sensor Return. Temporarily disconnect the speed sensor from the machine harness at either of the connectors shown below. These are the connectors right by the motors. Connect your meter between the terminals of the yellow and the white wire at the machine side then power on. You should see 8v. Repeat the process for the sensor on the other side of the machine.
Working on the same issue. Is anybody still out there? What do the sensors cost and what is the p/n#? I am having a devil of a time using the Cat online parts look up. Probably me but I can’t get it to recognize serial number or description of part.
I can find the Part Number and the last time I saw a price it was North of $300 per sensor. The thing is you may not have a defective sensor, it could just as easily be a wiring harness fault. Start with a Serial Number please. What S/N are you putting into the Parts system (parts.cat.com I assume?) that it won’t recognize.? Then give some details of the problem symptoms. Have you have accessed Diagnostic Codes yet.?
Using last 8 digits
Here is the alert.
E695 is a consequence of 2687-8. Does your machine have the Advanced (digital gauge) Display on the RH instrument panel.?
I downloaded your troubleshooting files from previous post. Just got in. I will dig around on the wiring later in the weekend. Just got the machine 10 hours on it so far.
It has the lcd screen display. 2018 model.
In that case.......... Press the soft key located directly under the "settings icon" (#40) on the screen. That should get you into the Main Menu. Scroll and find the "Service" section and then to the "Diagnostics" sub-menu. AFAIK it should have 4 sub-sections - Active Diagnostic Codes, Logged Diagnostic Codes. Active Events, & Logged Events. First check for any Active Diagnostic Codes or Events. Then go to the sub-menu for the Logged Codes/Events. Take a note of everything that is listed there and post back with your findings. Logged (non-Active) Codes/Events can be just as informative as Active ones.
Will do. I will get back to it tomorrow. I can’t recall the settings icon being displayed on the analog gauge screen.
Thanks for the reply and the help. I do remember scrolling through and finding service intervals. I will dive in tomorrow b
Hold up. Do you have a RH panel as per the image below with 3 buttons below the LCD screen.? If you do then the procedure for getting at the Diagnostic Codes is different.
No sir. My screen looks like the first screen you posted. It has the soft buttons across bottom. 7 buttons I believe.
I will post pics tomorrow.
OK, then in that case my instructions a few posts further up should work.
Pulled up diagnostics. I had one event around fuel leakage when I first got it but it was running out of fuel. Had one on water in separator. Drained that. The last two were related to drive motor speed. 2687-2 was first chronologically.
I suggest that you should keep that bowl well-drained. The High Pressure fuel syustem on that engine DOES NOT like water. I also suggest you need to drain water & sediment from the tank if you don't know when it was last done. There is a procedure for it in the O&M Manual. Attached is the troubleshooting procedure for the 2687-8 Diagnostic Code. NOTE the comment that even when the cause of the Code has been found and fixed the machine as to be driven for some distance to create a "good" sensor signal before the Active Code is cancelled.
I will dig into it Monday. No rest for the weary. With it throwing alerts in both sensors does that sound like a crimped or cut wires? Possibly through the window in the frame. Will I need to pull tractor assembly back to access sensors?
No it’s only throwing a DC for one sensor. Both Codes you see refer to the RH #1 sensor. 2687 refers to the RH #1 sensor, 2688 to the RH #2 sensor. There are 2 speed sensors in a common housing on each side of the machine. It could be a wiring issue, it could be one half of the sensor has gone AWOL. Carrying out the tests in the procedure in order will indicate where the problem lies.
Apologies I should have made it clear that Codes you have (2687-2 & 2687-8) both relate to the same sensor that is one of two mounted in a common body. Attached is the troubleshooting procedure for the 2687-2 Code but you will find for the most part it is common to the one I posted earlier.
Got it. Have to replace my Fluke meter. It has gone sideways on me for some reason. I will open the machine up and clean it tomorrow hopefully.
Make sure that your replacement DMM has the capacity to read duty cycle. You may not need it on this diagnosis but there are a lot of PWM sensors on that machine (e.g. these speed sensor, joysticks, etc) and the DC capability will surely come in handy at some point.
Kinda Greek to me. I do good to read AC vs DC. Running 10 hours and working on it for days isn’t what I signed up for. But I will get through it.
You'll find the duty cycle measurement (on a Fluke anyway) operates on the same key as frequency (Hz). With the meter set to measure AC voltage press the Hz key once and the RH side of the LCD screen will show a Hz symbol. Press the Hz key twice and the symbol will change from Hz to % which is how Duty Cycle is measured. A short tutorial follows on what the output signal of a PWM sensor looks like............ The duty cycle of a PWM (Pulse Width Modulated) sensor is measured versus time. See the illustration below that shows what the sensor output signal looks like at 10%, 50%, & 90% of the sensor Duty Cycle. Note that the only thing that varies is the "ON" time (grey shaded area) vs the "OFF" time (white shaded area). There is no change in voltage on the signal wire. The "height" (red arrow) of the square wave is proportional to the voltage in the sensor signal wire - not to be confused with the stabilized voltage supplied to the sensor by the ECM. That voltage does not change and it confuses the heck out of people when they measure it.
Model # for Fluke meter with that feature?
Fluke 87 is the one I have. There will be other models with the same feature I’m sure.
Just curious if the sensors are working properly what dynamic are they monitoring and why?
They are monitoring the drive motor speed in RPM. The reason that there are two of them per side is in case one fails the machine will still move using the signal from the other. It's the same reason the engine has two speed/timing sensors, redundancy.
Yes sir I understand they monitor speed but what is that signal used for? Does it have anything to do with two speed function, snail mode?
It is a feedback signal to the ECM so that, along with the position signals from the joysticks, and the signals from the ECM TO the hydrostatic pump solenoids, the machine ground speed can be controlled based on the operator joystick signal input. The propulsion system on this machine is 100% fly-by-wire.
Excellent.
Fluke 87 V ?
That’s what I have.
Ok. Guess I will FleaBay one. I want to be able to talk apples to apples. Your help is greatly appreciated.
Fluke 87-V on the way.
Have a Fluke 87-3 and also a Fluke 87-V. Good meters used almost daily to check all kinds of stuff. Just 1 battery is worth $200-400 and these meters have saved me buying one for nothing many a time. My 87-3 is twenty one years old this year and still going strong. No regrets. Simon C
Got the machine power washed down. Raised the cab and cleaned belly pan best I could. Still waiting on meter. Looked at plug for speed sensor. Thinking I could take a 4 male and 4 female Deutsch pins and crimp one of each on a 2” length of insulated wire. Plug them in to the connectors to complete all 4 circuits and meter each one with power on.
Or get yourself a set of "spoons" for the end of your meter test leads that allow you to back-probe into the connectors without disconnecting or having to fabricate anything. Google "Caterpillar 7X-1710" (other brands are available)
Spoons on the way.
Don’t ever buy a used meter off flea bay…….
Finally got my bad meter returned and a replacement here with spoons. Getting ready to get back on this machine after track replacement on my CT322. Not been a good month or two for skid steers. Question. As I troubleshoot this wiring for the hyd drive sensor. Any problem with leaving key switch on for longer periods as I have to raise cab up and down to power on and off? Just trying not to create some other issue. TIA
Should be no problem to power up and then raise the cab.
Ok. Not too good at this but bear with me. Disconnected RH drive sensor from machine harness. Sprayed with Contact spray and blew out with air. Still getting alert. Disconnected harness. Powered up and checked yellow wire to ground. 7.99volts. Protocol says to check white wire for 8volts. My first stuck place. White wire is return and with harness disconnected how would it have voltage?
OK, that's Step 1 and it proves the sensor has the correct power. Step 2 is to check for an open signal circuit wire.. Refer to troubleshooting procedure. It is a pdf file attached to Post #23 on the previous page.
Here is where it was confusing… Test Step 1. CHECK THE POWER AT THE SENSOR A. The machine harness remains disconnected from the sensor. B. Turn the key start switch to the ON position. C. At the machine harness for the sensor, measure the voltage. Measure the voltage from contact 1 wire (P769-YL(Yellow)) and contact 2 wire (P770-WH(White)) I made an assumption it wanted to check 8vdc to ground. I also figured no way I would get return voltage on the white wire with the harness disconnected. I spooned the machine side of the connector at the white wire and got 7.74 vdc to ground with the connector connected
As you discovered that’s not the case. The nominal 8v is generated inside the ECM and has a dedicated return/ground wire back to the ECM rather to the machine frame ground. This is also where your spoons prove to be very useful.
Clear as mud right now. Connector disconnected. Reading machine side. I read each wire to ground. What is it wanting me to do? Read between yellow and white?
As I move to the next step how do I locate/ isolate the plugs at the ECM?
I'll send you an electrical schematic that in addition to the wiring also has machine locations on it. The procedure says to put a jumper between Pins 3 & 4 at the sensor connector to make the two signal wires all one circuit but you can just as easily do the test in 2 steps without a jumper as follows: - 1. Disconnect connector J2 at the ECM. 2. Check continuity between J2 Pin 42 and Pin 3 on the sensor connector (wire 833 Grey) 3. Check continuity between J2 Pin 41 and Pin 4 on the sensor connector (wire 832 Brown)