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JLG 600S no throttle actuation

Oerthedge21 ยท 2025-10-07 15:39

Wondering if anyone has any input on this thing. It's a 1999 600S with the 4 cylinder Ford gas engine. Runs fine, and all hydros work, but there's absolutely 0 throttle ramp up. I've tested the actuator and it moves to full throttle when ground is applied to the terminal, and returns to idle then removed. Linkage and carb are smooth and free, no binding. The PG engeneering E331 computer is what I suspect to be bad. It has power, ground, wiring is good to the actuator, I have between 5-30v on pins C and D of the 8 pin connector for speed signal when running. The foot switch is newer, one of the control cards is new, and everything lights up and seems to work when the pedal is depressed. When cranking the starter also engages erratically, it'll kick in and out despite the switch being held, a function that is ran thru the E331 control box. Only problem is they're ~900$ to replace, so before I go changing it is like to be sure, but I can't think of much else to test. As it is all functions work when the machine is running, it's just deathly slow as it won't go about low idle.

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