JLG Boom Lift 23 Fault Code: Problems with Boom Function Selection
Also called Not Used
Problems with Boom Function Selection · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Fault code 23 on JLG boom lifts (M600) covers a group of boom function selection faults: joystick center tap out of range, boom functions selected before enable switches close, or pump pot/switch circuit problems. It is not a single failure but a family of related issues affecting lift, swing, telescope, and other boom controls.
Medium severity. Code 23 does not describe an engine or hydraulic damage risk, but it can disable or restrict boom functions (forcing creep speed or blocking movement entirely), which affects safe operation. Diagnose before continuing platform work.
What does JLG Boom Lift error code 23 mean?
JLG fault code 23 groups several distinct problems, all tied to how the machine's controller reads boom function selection inputs, joysticks, switches, and the pump pot potentiometer. Rather than one root cause, this code is a catch-all for selection logic and sensor range faults on lift, swing, telescope, basket level, basket rotate, and jib functions.
One set of causes involves the lift/swing joystick: if the center tap signal is out of valid range, or the wiper wire is open, the controller cannot trust the joystick position and sets code 23. Another set involves timing: if a boom function or the upper lift/swing function is selected before the foot switch (FWS) or emergency stop (EMS) circuit closes, the controller locks that function out and flags the fault.
A third group covers the pump pot potentiometer. If it goes open-circuit, all platform boom functions except upper lift and swing are limited to creep speed. Finally, if a boom function's switches show both directions selected at the same time (for example lower lift commanded up and down together), the controller treats this as a conflicting signal and sets code 23.
Common causes of 23
- Lift or swing joystick center tap output is out of valid range, or the wiper wire is disconnected (wire-off)
- Upper lift or swing function was selected before and during foot switch (FWS) closure, locking out the function
- Pump pot (potentiometer) is open-circuit, forcing all platform boom functions except upper lift and swing to run at creep speed only
- A boom function (lower lift, telescope, basket level, basket rotate, jib) has both directions selected at the same time
- A boom function was selected before and during foot switch closure
- A ground-side boom function (lower lift, telescope, basket level, basket rotate, jib) was selected before the key switch was turned on
- Swing joystick center tap out of valid range, or wiper wire-off, treated the same as the lift/swing joystick fault
How to troubleshoot JLG Boom Lift 23: first checks
- Cycle all joysticks and function switches to neutral before engaging the foot switch (FWS) or key switch, then retest to rule out a selection-before-enable lockout
- Inspect the lift/swing joystick wiring and connector for the center tap and wiper circuits, looking for corrosion, loose pins, or an open wire
- Check the pump pot potentiometer wiring for an open circuit if platform functions other than upper lift and swing are stuck at creep speed
- Verify boom function switches (lower lift, telescope, basket level, basket rotate, jib) are not mechanically stuck or wired so both directions can close at once
- Run onboard diagnostics to identify which specific sub-condition under code 23 is active before replacing any component
How the code clears
No separate clearing step is listed. Because code 23 covers several distinct conditions, correcting the specific cause (releasing the joystick or switch to neutral before enabling the foot switch or key switch, repairing an open wiper wire, or fixing a stuck switch) should allow the controller to clear the fault once the input returns to a valid, non-conflicting state.
Affected models and serial ranges
23 appears in our records across 1 JLG Boom Lift models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| M600 | Serial range not listed in source records |
Frequently asked questions
What does JLG fault code 23 mean?
It signals a problem with boom function selection on the M600 platform. This can be a joystick signal out of range, a function selected before the foot switch or key switch enabled it, an open pump pot circuit, or conflicting switch signals on a boom function.
Why are my boom functions running at creep speed only?
If the pump pot potentiometer is open-circuit, the controller limits all platform boom functions except upper lift and swing to creep speed as a safety fallback.
Why won't my upper lift or swing function work?
If upper lift or swing was selected before and during foot switch closure, the controller locks that function out until it is returned to neutral and reselected properly.
Can a bad joystick cause fault code 23?
Yes. If the lift/swing joystick's center tap signal is out of valid range, or its wiper wire is disconnected, the controller cannot read a valid position and sets code 23.
Is fault code 23 dangerous to keep operating with?
It is not listed as an engine or structural damage code, but it restricts or disables boom functions, which affects safe platform control. Diagnose it before continuing lift work.
Does fault code 23 always mean the same failure?
No. It covers multiple distinct conditions: joystick faults, selection-before-enable lockouts, pump pot open circuits, and conflicting switch signals. Use onboard diagnostics to identify which specific condition is active.
How do I clear JLG fault code 23?
No separate clearing procedure is listed. Correcting the underlying cause, such as returning a joystick or switch to neutral before enabling the foot switch, or repairing an open wire, should allow the fault to clear on its own.