I've owned this 490e machine for approx. 10 years. Twice - when the machine had been ran for several hours straight, the hydraulics would load up the motor (during any/all functions). If I walked away for an hour and the machine cooled off, everything would return to normal operation. Now it seems to have failed and will not go away. All functions are effected but work if the controls are moved very slow. It also seems to have a continuing small load on the hydraulic system/engine at all times. When started and left idle, the engine temp seems to be higher than it should be as if the hydraulic oil is heating up. I have not called a dealer for help at this time. Just want to look into it before I call. Any suggestions will be greatly appreciated. Thanks.
Welcome to HEF Martin ! Swap the 2 solenoid assemblies (solenoid and the block they are attached to) on top of the main hydraulic pump to see if the problem reverses (little to no hydraulics). If that happens then one of the solenoids are defective.
swapped both solenoid assy's - problem still exists - except now it continues to load the engine very heavy but doesn't kill it. also, when I jumped the diagnostic connector - the hydraulic controller is flashing many codes that do not exist in the JD book.
I own a 490E and fought the problems like you describe for years. Mine would eat angle sensors regularly and DP sensors as well. It also took out some main control solenoids. The machine was weak and plagued with overheating issues. If I were you, I would first check the angle sensor electrical output setting (4.40 V + or - 0.05). If it is OK, then check the DP sensor output. The book says 0.4 V for the DP but Deere Solutions recommends a 0.8 V for dirt diggers. (The lower the DP setting, the faster the machine calls for pressure from the Main pump.) If you don't find your issue with these above actions, I would move to pressure checks on the main pump. Depending on your serial number, it may have a surge relief and a main relief which are not difficult to check and adjust if needed. If they are good, then move to the pilot system to check and adjust the pressures there with respect to pressure regulator and pressure controller. It took me 6 years to finally find the problem with my 490E. The computer was giving me nonsensical codes too. It turned out to be a fault to ground in the power supply wire to the computer from the main fuse block. Does your machine blow the 1A computer fuse occasionally? The factory harness has a cheesy splice in it which was not insulated where it split to make the two connections at the computer. I found the fault to ground with a meggar, replaced the wire and it solved my problems.
To ALL The hydraulic issue I had turns out to be 3 broken wires to the hydraulic relay . We made the repairs and all seems to be OK. Crazy how those three wires caused 10-15 fault codes, most not list in the book, as well as killing the motor. Just thought I'd pass this along. In a few months I will likely be selling this 1997 490e. If anyone is interested let me know. It's in south central Illinois.