I've got a few issues showing up on my Cat 320DL, serial SPN00784, that started the same morning on a machine that doesn't run very often.
First problem is that the travel speed and auto idle functions both stopped working. The green lights on the button control panel are on for both, but the speed light won't change to high and the auto idle light stays on all the time and won't turn off—though auto idle itself isn't actually working. A tech came out and traced the wiring, and the ECM is definitely receiving the signal that I'm pressing the buttons. From what I understand, the ECM is supposed to send a signal back to make the functions change, and that's not happening.
The second issue showed up later that same morning: the swing brake locks up randomly once I stop the control or at startup. It was sporadic at first but now it's happening almost every time. I can toggle the fine swing control off, and if the swing was working properly to begin with, the machine runs the rest of the day with no brake just fine. Sometimes toggling it off unlocks the brake fine. Other times when the brake is locked and won't unlock like it should, toggling the switch doesn't help either. Restarting the machine always unlocks it. I'm thinking about trying a solenoid.
Everything else works—AC, radio, lights, all good. We've checked the battery voltage and it's fine, but there's one odd thing: the machine monitor is only showing 0.5 volts in its readout. I'm not sure if it's always done that.