Cat 279C2 Drive Problem

[torey driver]

I have a Cat 279C2 serial number AT0279CTKWB00583R that has a drive problem. If you drive forward slowly it will move forward. If you stroke the joystick more it locks up the left track. If you slowly go in reverse it will ease backward but will lock up the right motor with more stroke of the joystick. It will eventually make forward go reverse and reverse go forward with the joystick. It has no codes active. I had a mechanic hook up to it and the numbers for the joysticks looked good. He ran a calibration test and it said left speed sensor code. Replaced left speed sensor and tried driving and same problem. Any help would be greatly appreciated. Trying to figure out if this is a hydraulic or electrical problem but seem to be leaning to electric.

 

[torey driver]

Forgot to mention machine seems to turn fine.

 

[Nige]

He ran a calibration test and it said left speed sensor code.

That makes no sense. There is no calibration for those sensors. Do you mean he ran a "diagnostic test".?

It has no codes active.

That makes even less sense based on the above comment "it said left speed sensor code".

Replaced left speed sensor and tried driving and same problem.

It might not have been the sensor at all but a problem in the wiring.

Do you know what the Code was.? I'm guessing it was either 2685-8 or 2686-8. There are test procedures to identify what the problem is before throwing parts at it.

 

[torey driver]

That makes no sense. There is no calibration for those sensors. Do you mean he ran a "diagnostic test".?

It must have been a diagnostic test. The machine had to be up in the air. It kicked out the test.

 

[torey driver]

Before the mechanic came we did not have any active codes until he performed the diagnostic test. After test 2685-8 was active. We ohmed out the 4 wires to the ECM and checked good. I have had a few 1706-5 in the stored codes but never active.

 

[Nige]

Here's the diagnostic for 2685-8. Hopefully it helps you find the problem.

 

[Nige]

I have had a few 1706-5 in the stored codes but never active.

To be a stored Code it has to have been active at some point. Interesting that it refers to the motor solenoid for RH side reverse direction. Maybe you want to dig into this one as well just in case. It could well be related.

 

[Nige]

Did the mechanic who hooked up to the machine use Cat ET diagnostic software or a different type of generic code reader.?

 

[torey driver]

Thank you so much for your time. I will go through both troubleshooting links above. The mechanic that came out works for Cat and I would assume it was Cat ET software but could not say for certain. Have you ever saw one that will all of sudden swap the forward and reverse direction using joystick? As in I push joystick to go forward and machine goes in reverse, I move joystick to reverse position and machine goes forward. It will do that several times then go back to the direction being correct.

 

[Nige]

The mechanic that came out works for Cat and I would assume it was Cat ET software but could not say for certain.

In those circumstances I would also assume that he had ET.
You could ask him did he find any Events logged on the machine. Events are slightly different to Diagnostic Codes but there might be something that gives a clue. for example something "unexpected motor speed detected" (there are 4 different versions of that) or "drive motor speed detection disabled".

 

[torey driver]

Sorry for the delay but I looked at machine today. I checked everything you sent over and everything checked out. On the form you sent it showed homing out 42 and 43 with jumper in but the schematic shows 41 and 42. Maybe just a misprint. See below.

 

[Nige]

On the form you sent it showed homing out 42 and 43 with jumper in but the schematic shows 41 and 42. Maybe just a misprint. See below.

The procedures can often be somewhat generic. Sorry I should have warned you. Always use the Pinouts as shown on the electrical schematic because it is always specific to the machine model. if you look .cposely you will also see that the wire numbers and colours are also different. It doesn't make the testing procedure wrong, you just have to be careful.

So in this case because it is the LH track that we are concerned with, the appropriate Pins on CONN J-2 are 35 & 40. You will see that Pins 41 & 42 are for the RH track speed sensor signals.

 

[torey driver]

Yes sir. While I had the ECM plugs off I went ahead and checked both sides. While trying to perform a solenoid calibration is when it will throw the code. There are no active codes but after trying calibration it fails to calibrate and will be in stored codes. Attached are pics of codes. I did swap the jumper harness so that may be why the code swapped from right to left. When machine starts driving opposite of the direction controller is moved the current to the solenoids shows the right direction but machine moves opposite Is it starting to sound like I may have a hydraulic problem instead of electrical?

 

[Nige]

That page full of Codes on your screen are all Logged Code. I suggest that the best way forward would be to erase all of them then run the machine and see which ones come back.

I would however suggest that before erasing anything you should download a Product Status Report in pdf format before proceeding further. See this link and make sure that you select "all available ECMs" before downloading - Download PSR

 

[torey driver]

I erased them yesterday and ran the machine. Could not get a code until I tried to calibrate solenoids. Then it came with the code pictured below.

 

[Nige]

Have you ever saw one that will all of sudden swap the forward and reverse direction using joystick? As in I push joystick to go forward and machine goes in reverse, I move joystick to reverse position and machine goes forward. It will do that several times then go back to the direction being correct.

Do you have a multimeter capable of measuring duty cycle.?
If you do then the first thing to do if it acts like that again is to check the signal output from the PWM sensors on that joystick and record the percentage values for neutral (centre), full forward, and full reverse on that joystick.

Could not get a code until I tried to calibrate solenoids.

Which solenoids were you trying to calibrate.?

The problem as far as diagnostics of the 2685-8 & 2686-8 Codes is that you need them to be Active for the troubleshooting procedure to work properly. Note that now you have a 2685-8 in addition to the 2686-8 that you had before.

 

[torey driver]

I believe it was called the fed rev solenoids.

 

[Nige]

I would suggest to postpone attempting the calibration for now and run the machine as it is.
Clear the Logged Codes from memory and see what comes back.

EDIT: Did the control lever calibrations at the top of the list work OK.?

 

[torey driver]

Ok. The joystick calibration goes through successfully. The machine is not able to be used the way it is. If you try to drive it, it will start driving and will lock up especially if you stroke the joystick too much. It will move for a little bit if you barely stroke the joystick. Turning seems to work good.

 

[Nige]

OK, let's go back to the top of the list. Try the calibration for the Throttle Position Sensor.
If that works OK, then try the (4 separate) calibrations for the bucket solenoids.