Hello everyone, I have a cat d4g lgp. Ser.#tlx00345. 7800hrs I’ve been chasing this issue for a while now. The machine likes jumping to the right, as in the left track speeds up up for a sec and slows down, constantly. If you let it go you’ll just go in circles. And it’s violent. Funny thing is, it only does it at higher speeds, or really high rpm. If you keep rpm like 3/4 and speed below 2, it runs fine. What’s been done. Both new speed sensors Both new speed solenoids New joystick New module under joystick Cat has calibrated speed and joystick Had a park brake switch code Left speed sensor code Left speed solenoid code. Over 2 hours ago these came up and have not come back. Cat was watching the live data and saw a voltage spike on the left drive everytime it started jumping. Stumped. Any help would be appreciated!
Upfront, I'm not an expert in heavy machine repairs but I've been around wire bundles and control signals enough in other industries to wonder if you have a rubbing short to ground or battery power somewhere that's causing a spike in your signal wire. Since Cat already diagnosed a random voltage spike, the only way I know how to 'troubleshoot' this is run two new wires from the main connector to your sensor. If it goes away, that was your problem. But I'd still wait for the experts here to chime in who should know more about your particular machine. Hopefully it's something simpler.
Kinda what I was thinking at first, but I assume it would affect it all the time as opposed to just higher speeds. I did move all the wiring around that I could reach all the way up past the hard bend it does on either side of the game while cat was watching the data, found no relation there. I have not chased wiring further than that
Yes rodents like a warm place to shelter and a dozer is just that, speaking from recent history of nests (bad - in the #5 belly plate) and chewed cables in the dash instruments, lucky not to cause a fire. Good luck.
A voltage spike on WHAT exactly.? Sensor output signal, solenoid input, what.?
Not exactly sure, I can ask him, pretty sure it was speed sensor
I didn’t know that ET could see speed sensor power. In fact I’m pretty sure that it can’t. Also ask him did he download a Product Status Report (pdf format) and if he did get him to send you a copy and post it up.
Okay let me ask him, see what he says, stay posted
Okay, he doesn’t have a pst. And Disregard voltage spike he doesn’t remember anything about that so I must have misunderstood. Only way I can get a psr is if I actually call them out again I guess
Downloading a PSR before and after working on any machine equipped with electronics is an SOP for all dealer service departments as far as I’m aware. You could speak to the service manager take them to task on that for a start. Maybe taking a look at Codes yourself might be the next step. See this thread where you’ll find the documents and an explanation of how to do it. HeavyEquipmentForums
Update to this thread, replaced the speed sensors once more and the problem was fixed, must have been one or two faulty speed sensors!
Thanks for the update. Question: Were the “new” speed sensors in the list of parts installed before you posted initially genuine OEM ones or aftermarket.?