Hi Guys, I'm a newbie here from the other side of the World but I'm having an issue that needs some outside expertise. I have a 277C with only 200 hours on it, but it is three or four years old. Last week it started showing a yellow exclamation warning on the left side top panel. I don't have the top right panel so no way to read codes. If the yellow light was on it would steer slightly to the left in the straight ahead position and you have to keep pushing it back. Really annoying. In desperation I purchased a CAT ET system and it has a code E568 and says left drive motor speed sensor #1: Erratic, Intermittent or Incorrect Then another one that says Left Drive Speed Sensor #1: Abnormal Frequency, Pulse Width or Period? Any clues as to what this could be? I've followed the wiring where it exits the lower side of the cabin and attaches to the hydraulic lines. There is a plug there and I removed and cleaned that but it was clean as can be inside. Very well sealed. There isn't any physical damage to the wiring that I can see. You can trace with your fingers and a mirror and see that the wires go into the back of a silver steel housing which is probably the speed sensor itself. Could loose tracks make one side go faster than the other and upset the ECM? I've only recently purchased the machine and done less than 20 hrs on it but I don't think it's even had it's first service let alone had the tracks adjusted ever. At first the light and beeper came up and stayed on until forward motion stopped and hand was off joystick. Then after a while it actually stopped the machine, no forward or backward motion just the bucket still operating fine. Turn off the machine and do a full restart and it came back again. Back to the shed with it, checked filters, air intakes, levels etc, topped up the hydraulics which were 8 liters down and cleaned the pre air filter which was nearly clogged with fine dust and I was sure that this would fix it but the next time it went out it repeated the same fault. Here's a picture of the screen dump created by the CAT ET.
Hi, lift the cab and swap the speed sensor plugs over ie right side plug to left side motor and report back DONT FORGET SERIAL NUMBER
Hi Mark250 It's a track loader machine so I'm thinking that the speed sensors are on the outside and tucked down behind the tracks at the motors. Seem to be horrible to get to.
yes they are ,but with the 2685 and 2686 codes it does point to the sensor or the wiring to that sensor ,I do know that at the back of the motor there is a cover over the sensor and the wires fray at that point . worth a check it is also worth while removing the sensors and check for damage or debris on the ends I don't mean to scare you but according to SIS that error code 0568 indicates large speed differences between actual motor speed and desired motor speed cat indicates that the primary cause of this code is pump failure do you also have an active E695 if you need help troubleshooting the sensor wiring please ask. some one will be able to help mark
Looks like some lost time over the weekend hunting this down. Definitely no active codes and never seen an E695 come up. Thanks Mark250, I'll go hunting a bit deeper.
200 hours, I think I'd call the dealer even it is a few years old and see if they'd cover it under warranty. 200 hours isn't even broken in.
Uzz, Do you have the Electrical Schematic for your 277C..? If not do you want one..? If yes send me a PM with your email address and your machine Serial Number.
Thanks to Nige for the electrical schematic. Today I spent hours trying to trace the issue. Cabin up, external covers behind the tracks off and then traced the wires from ECM to sensor on both sides. The right side cable was beautifully placed in a cleft created by the two hydraulic lines. Well protected and laid. Left side was a mess. Wrapped around hydraulics, more exposed, clearly no care placing that when the machine was wired. Off with the cable ties and lay the look properly and inspect every cm at the same time. Pop off both plugs and they were perfectly clean, not even a spec of dust had penetrated the plug seals. The sheath close to the sensor was wrapped around the hydraulic fitting and then went down to the sensor but there were two small perforations in the sheath close to the large hydraulic nut. I pulled the sheathing back and couldn't see any damage to any of the four wires though. Once I was happy with everything, I closed up the machine and tested it. I also found that the tracks were about 24mm and 28mm slack and should be 12 - 14mm with a 45kg load so I adjusted these at the same time and did a full grease job. I barely moved the machine before I got the dreaded ! warning and the damn beeping. Instantly the machine slewed to the right and was difficult to straighten. 200m of driveway improved the handling a little but it still pulls left and even after multiple restarts the ! warning and beep don't go away. My CAT ET interface unit comes up with the same error but this time the error is active and can't be cleared. So it appears that I may have had a dodgy wire or sensor and moving things has made it worse and now it's plating up constantly. Bugger!! So looking at that sensor via a telescopic mirror, I tried and tried to get a tool on the head of the retaining cap screw but to no avail. Unless there is some crazy tool it appears that either the main hydraulic feed needs to be removed or the motor slid out to allow clearance to get an allen key in there. A two minute job on a wheeled machine looks to be a nightmare on a tracked machine. Without an SIS I'm a bit stumped as to how to replace that sensor. Impossible to think that Caterpillar would not design that sensor to be inaccessible when it's clearly a serviceable item? Has anybody here actually done one that can give me a pointer or three? I'll order a new one tomorrow. I'll check with Cat in Melbourne but I'm thinking that it's going to be prohibitively expensive and I may have to get one from the States. Seems that the part number is 2623764 and it looks like the attached image. Would anyone with a parts manual care to confirm the number for me please?
Image of speed sensor. Tried three times. Sorry I cant upload the image. It's only 77kb but it wont load.
Well thanks to Nige I've managed to repair the Beast and get back to work. Thought I'd write a little info here for other guys who may be in a similar situation with a wheel speed sensor fault. Here's a few notes to take on board before going out and spending your hard earned cash on a new sensor. Everything I looked at on my machine indicated a faulty sensor. Especially when I checked all the loom, popped and cleaned all the plugs, and then the machine failed with lights and bells on all the time. So back to basics care of an SIS bulletin from Nige. It was a fault in the harness. Coming from the ECM the main loom breaks down the farther it gets into the machine. The speed sensors break away from the main loom at two plugs. Then each side has a short 650mm plug to plug loom with the four wires in it. These looms exit the sides of the machine and plug to the sensors. I started out inside the machine at the entry to the first plugs from the ECM and had 8.14v on both sides of the plug. Checking the white wire to earth and the yellow as power. I opened them and gave them a shot of contact cleaner for good measure and then closed them up and went farther down the line. No power at the sensor connector on either side of the plug? So I removed the 650mm loom and started looking at it properly. I exposed wires at the back of the plugs and ran continuity tests with zero results. So I had to strip that four wire loom down, replace the wire 30mm from each plug end. Re-sheath and refit the loom and test again. 8.14v at the sensor. Serious wiggle test stood up and voltage didn’t change. Fired it up and error and beep still was there so backed it out and drove around the shed and did a couple of pirouettes but the error stayed. Had to clear some scrub quickly so started towards that and about 30m later the error code disappeared and never came back. Tomorrow I’ll connect it all up and code check and clear but it appears to be a happy little machine again. It was a bit tricky. Four wire harness with no numerical markings anywhere but white / purple and two yellow wires. One with 8.14v and the other with 5.27v? Who else but Caterpillar would do that? So if you ever get this error, look first to checking that you have an 8v +/- 0.5v reading to the sensor. Then there are some other Ohm readings to check and verify before you go out and order a sensor. In my case, who could imagine on a 200 hour machine that a wire could separate inside a protective sheath where it doesn't even rub on anything. Strange thing to hold a length of wire 600mm long and run a continuity check on it with a zero result. You look twice and just go "***?" to yourself. Sure goes to show that it's useless simply replacing parts on a whim without doing the diagnosis correctly first to determine exactly what's wrong. My issue cost me a few lost hours but I was able to repair it myself with zero cost and zero parts. Thanks again to Nige and other members here for their valuable input.
That short jumper harness is shown in Grid A-12 on Sheet 1 of the actual Electrical Schematic for the machine. It's titled "MOTOR SPEED SNSR MTL JUMPER" and is an Attachment. According to the schematic the wires (white, purple, and two yellow) should all be numbered. P769 (YL), P770 (WH), 834 (YL), & 835 (PU). Maybe the numbers are hidden further up the jumper, usually they are repeated every 250mm or so in the length of every wire in a harness. The jumper harness is readily available - indicating to me anyway that it has been in demand - maybe due to failure, who knows..? The Part Number is 258-4158 and it retails at US$51 should you ever decide it requires replacing. This compares to almost $200 for a replacement speed sensor. It's known in the trade as a Cat Design Feature - designed to ***k you up .........
Hahahahaha....................sure is! Those wire numbers must be smaller than my old eyes can see. I looked and couldn't see anything on the wires, hence the issue with the two yellows carrying different voltages.
Here's what the manual says. As I suspect this is a PWM (Pulse Width Modulated) sensor. Basically it produces a square waveform signal and the width of the signal wave is directly related to the speed of whatever the sensor is measuring. The sensor produces a digital signal with a duty cycle that varies as the condition changes. The frequency of this signal is relatively constant and the frequency contains no information. Below is a graphic showing what the square wave from a PWM sensor looks like for 10%, 50%, and 90% duty cycle. Also I cleared up another question - the sensors #1 & #2 are both in the same housing which explains why there is physically only one sensor but there is a common power feed and return, so if Diagnostic Codes come up for both sensors the logical culprit is either the power or the return. The sensor is fed with a regulated DC voltage produced by the ECM, therefore between P769 (power) & P770 (return) the voltage should be 8.0+/-0.5V DC. The wires 834 YL & 835 PU are for the digital sensor output signals therefore any voltage measured between either of those wires and any other wire will be meaningless.
Hi Nige, the beast has been behaving well since finding that broken wire and repairing it. Just one issue. I'm getting an hour glass popping up next to the hour meter. It started at about 240 and now still there at 260. Not all the time but I suspect its there about 80% of the running time. I figured it might be a reminder that the 250 hour service was due but I did the service and then went in to my CAT ET to input the service data and can't find anything there that indicates a service warning code clearance. Any idea what this could be. Just a small hour glass symbol next to the digital hour meter.
This is what the O&M Manual says and I'm buggered if I can understand it. When it refers to the Digital Display window it means the window in which the Hour Meter reading is displayed. The left side Digital Display window displays the Service Hour Meter (SHM). The SHM displays the hours of machine operation. This feature is also referred to as the total operating hours of the machine. Use this display in order to determine the service hour maintenance intervals. The functions of the SHM are listed below. The functions of the SHM in a system without a synchronized system clock:- The following will occur when the speed of the engine is greater than 150 RPM or when the frequency at the alternator R terminal is greater than 20 Hz: Hours will accumulate in tenth hour increments. Hours are logged in 6 minute intervals. The following will occur when the speed of the engine is less than 200 RPM and when the frequency at the alternator R terminal is less than 50 Hz : The hours will retain the currently stored value. When the maximum value is reached, the maximum value will remain in memory until a reset is performed. Cat Electronic Technician is used in order to make a reset. The functions of the SHM in a system with a synchronized system clock follow: The SHM will operate within the requirements of the synchronized system clock. Note: The C model Steer Skid Loaders support the synchronized system clock.
Clear as mud isn't it Nige. So it appears that I have a synchronized system clock whatever that is and that clock is synchronized to my Service Hour Maintenance intervals. This sort of makes sense and I suspect is why I'm getting the egg timer symbol as it came up before the 250 hr service and is still there even though I've done the service. There must be some way to tell the machine that the service has been completed but if it's in the CAT ET then I can't find it.
I know it might sound kind of counter-intuitive but have you tried asking your dealer..?
I'm having the same problem...mine is a 289c though. JMP01627. It will start out fine but immediately slows and yellow ! and alarm comes on when moving left joystick. I lifting the cab, checked wiring, everything in this post. I have 8V to both sensors. Code 2685-8 when error comes on. After cleaning sensors and connections, went to test it. Everything worked fine, no sluggish, no alarm. As I was backing up to turn around, the alarm came on again and won't go out (just as before)...I dont understand if i have 8v to both sensors why is it still giving me an alarm. I also put two brand new sensors in it. Any ideas, Thanks.
Everything points to the signal from the speed sensor for the LH drive motor. Diagnostic Code 2685-8 will only be active if you operate the left joystick to command the LH drive motor to move. When the motor is not moving there will be no diagnostic code so that explains that part of it. The issue with your Diagnostic Code is not the supply voltage to the sensor but the PWM signal that the sensor is sending to the ECM. FMI 08 indicates "Abnormal Frequency, Pulse Width, or Period". FMI 08 occurs when the frequency of the signal or the pulse width of the signal is not within the range that is expected by the ECM. CID 2685 is the Left Drive Motor Speed Sensor #1. I would be looking very carefully at the 834 Yellow wire that takes the PWM signal to the ECM from the #1 speed sensor. See post #13 on Page 1 for more explanation.
I tested all the wires for continuity, all check good. Just fired it up again and tested it, it ran without the warning or alarm and then it came back on. Im also feeling a pull to the left...if the left drive motor was not turning at the same speed as the right, it could throw the code for the sensor correct? im replacing fluid in drive now.
I don't think so, because when you want to turn surely one motor has to move at a different speed to the other, right..? So as I see it the signal from the LH & RH speed sensors is going to be different at anything other than moving in a straight line. You will note that there are 2 separate speed sensors on each side (#1 & #2), despite the fact that there is physically only one sensor body. The power supply and ground wires are common, the signal wires are separate (see post #13 on page 1). So if the LH sensor #2 is not throwing a diagnostic code, and you say you have replaced the LH sensor assembly with a new one (thus ruling out the possibility of a dodgy sensor), then the only possibility as I see it is that something is wrong with the signal side of the LH #1 sensor. That's different to the situation where both sensors on one side are giving Diagnostic Codes at the same time then the problem could possibly be in either the power or ground wires - or both signal wires. But one sensor only seems to indicate something in the signal wire. I'm not 100% sure that a pure continuity check will show up a problem. Have you actually physically checked the signal wire for damage right the way from the sensor to the ECM..? Also I'd suggest to have a very close look at the male & female pins inside each Deutsch harness connector to eliminate the possibility of a bad connection inside a connector on that signal wire caused by a loose or misaligned pin. The pins push into the connector and are retained by a pair of plastic "ears". If the ears don't grab hold of the pin properly then when the 2 halves of the connector are joined up it can physically push a pin out by a hair and leave you with a bad contact.
Ok, thank you. Ill check that tonight..
If you want a copy of the Electrical Schematic then send me a PM with your email address.
So i checked every wire from the ecm to the sensor. Everything checked good, only one last thing to do....i swapped the sensors from LH to RH. Tested it in the yard and was all good for about 10 minutes. And its back. This time with the 2687-8 code. All points to faulty sensor. Which is a big surprise considering its brand new.
If the same Diagnostic Code moved from one side of the machine to the other when the sensors were swapped then the only possible conclusion IMHO is a bad sensor. So long as you still have the delivery paperwork take it back and exchange it for a good one.
Swapped with new sensor and runs like a champ. Thanks for your help Nige!
Nice to hear it's fixed. TBH it fooled me when you said earlier you'd put a new sensor on it, one would assume that a new sensor would work correctly. That assumption kind of sidetracked the diagnosis process.
speed sensor 277c Nigl, I need a wiring diagram for the 2008 277c, I have speed sensors problems. I replaced both sensors and still have the problem. Please help. Thanks Dabo1
Post a Serial Number so that I can find the correct schematic and you're welcome to it.
Serial # Jwf01905
Hello I am glad I stumbled on this forum I am having the same issue with my 2016 239D it started about a month ago it has 300hrs on it and I bought it new the salesman I bought it from told me to check the grounds first before I brought it in which was ok with me as it would probably sit there for 2 weeks before they did anything to it but anyway today I lifted the cab and washed it all out and cleaned it up and was checking the grounds for any loose connections and I didn't find any so I found you guys here and started reading so I went to my shop and the first thing I did was check the connections to the speed sensors I took them apart sprayed them with contact cleaner the took the air hose and blew them out and knock on wood It may have fixed it I didnt get to run it much this evening to really check it out but I will tomorrow and if it does it again I will come back and see if anyone has any suggestions but so far so good thanks for the input to others as it was very useful to me James
HELLO I
HELLO I HAVE A 2008 CAT 277C WORKED GREAT UP TILL COUPLE DAYS AGO. WITH 8' SNOW BUCKET IN MID LIFT THE YELLOW EXCLAMATION POINT OF DEATH CAME ON AND HYDRAULICS TO LIFT AND BUCKET, IT QUIT ! ! THE TRAVEL STILL WORKS. 1) IS THERE A GOOD SET OF WIRING DIAGRAMS. 2) IS THERE A BEST PRACTICE AS TO EFFICIENTLY RIP & TEAR TO FIND WIRING ISSUES 3) I HAVE THE ERROR CODES. IS THERE A LIST OF ALL COMMON CODES AND EXPLANATIONS 4) CAN I CLEAR OLD CODES, TO TELL WHICH MAY STILL BE ACTIVE ISSUE MACHINE HAS BOUT 9500 HRS ID#CAT 277C JJW501587
Your Serial Number appears to be incorrect - JJW is a D10T. Are the last 8 characters of the PIN JWFxxxxx.? Correct Electrical Schematic will be determined by the Serial Number. What Diagnostic Codes do you have and which of them are Active..? Post a list. Just FYI, there's no need to shout. Using caps is considered shouting on a forum such as HEF.
*CAT0277C JJWF01587* OOOPPS ! ! THE #5 KEY AND UP ARROW 2475-3 2477-3 ACTIVE ????? OLD ????? HOW TO TELL IF OLD OR CURRENT? CAN RESISTER BE CLEARED TO ONLY SHOW CURRENT ITS A 2008 9500 HOURS DOUBT ITS EVER BEEN CLEARED BEFORE
Your Codes both relate to the position sensors for the RH joystick. One is for the front/rear sensor, the other for the left/right sensor Attached are the Troubleshooting procedures for both Codes. I'll send you the Electrical Schematic separately.
THIS WILL BE VERY HELPFUL THANK YOU VERY MUCH
Hi, I have a 257D that is throwing the right #1 and #2 warning E570-2 and E570-1. There's also a red warning that comes up about unexpected speed protection not engaged, speed will be limited, but it isn't limited at all. So, I traced the wire to the drive and checked the voltage from yellow to white at the 2 points where it appears you can disconnect them (under the cab where it splits from the loom and just outside under the shroud where it connects to then finally go to the drive. At both places I have 8V on yellow and white. On the other 2 colors to yellow I have 5V and 3V respectively, which would indicate that there is something on there. (PWM I would assume) which indicates to me that it isn't the wiring, but the actual speed sensor unless it could be way up on the back wall where there is an issue, but then I wouldn't be getting 8V and the other two wouldn't be getting anything I would think. I've cleaned all of the contacts anyhow to no avail. One stupid question before I spend lots of money, could it be that the error codes are firing because the wires are backwards to each drive? (the color code is Purple on one and brown on the other, but to the drives they're both purple...) If it could just be switching them, then cool. So I'm left to assume that it's the sensors on the drive that are screwed. But damned if I can figure out how you take it off without dropping the entire track and drive unit off the axels (not my idea of fun without another piece of equipment to lift them back on, which I don't have). Does anyone have the procedure for how to get the sensor off the drive? Any pictures? I can barely see with the track slid as far as it will go off the axel before it falls off, so I can't tell what I'm working on. Thanks in advance!
Try a Serial Number first (8 models to choose from), then answer a question - do you have an electrical schematic.? If your DMM has the capability of measuring duty cycle you can measure the PWM signal from the speed sensors. A comment. It may well be that at some electrical connectors (especially at sensors) the wire colour/number on one side of the connector is different from what's on the other side.
I have a 277c and would like the wiring schematic for the speed sensors too please serial #JWF01719
Is there anyway I could get a copy of the electrical schematic? I know this was several years ago but pretty desperate