What could cause a John Deere 490E to stall when hydraulics hit relief, esp with low or no voltage going to most pump sensors and weak tracking?

[Nicholas Villa]

I am looking for some help/insight on a John Deere 490E stalling issue I'm dealing with. The machine starts and idles fine, but as soon as I run any hydraulic function all the way to relief, the engine bogs hard and stalls.

Here's what I've checked so far:

• Getting 5V at the pressure and angle sensors
• Only about 0.2V at the speed sensor
• 0V at most of the other pump solenoids/sensors
• All fuses look good
• There's a steady blinking light on the computer under the seat
• The throttle has been rigged with a cable (factory control not working)

From what I've read, it feels like an electrical/control issue-maybe something with the pump controller, wiring harness, or even the ECU not sending proper signals?

 

[jonathan Morris]

Sounds more like the pump control system isn’t destroking under load. The 0.2V at the speed sensor is suspicious, and the cable-rigged throttle could also be confusing the controller.

 

[MichaelThompson]

Honestly sounds more electrical/control related than a straight hydraulic failure to me. I had a Deere excavator years ago that acted almost the same way and it ended up being a bad ground and damaged wiring near the pump controller. The machine would idle fine, but as soon as hydraulics loaded up the engine couldn’t compensate correctly and it would bog hard.

With you only seeing 0V or very low voltage at multiple sensors/solenoids, I’d spend some time checking power supply, grounds, and harness continuity before replacing hydraulic components. The blinking light under the seat might also be pointing to an active controller fault.”

 

[randdyarroyo]

If it stalls ONLY when hitting hydraulic relief, I'd suspect the pumps are staying fully stroked because the controller isn't getting proper feedback.
0V at most solenoids/sensors is not normal. I'd start with:

• Controller grounds
• 5V reference short somewhere
• Bad pump controller
• Broken wire in harness near pump
• Failed engine speed sensor signal

I've seen Deere excavators do similar stuff from bad grounds alone. Load the hydraulics and voltage-check grounds under load, not just key-on.