JLG Scissor Lift 23 Fault Code: Level Sensor Failure
Also called Function Locked Out - Ground Aux Switch Permanently Closed, Function Locked Out - Ground Front Deck Ext Permanently Closed, Function Locked Out - Ground Front Deck Ret Permanently Closed, Function Locked Out - Ground Lift Down Permanently Closed, Function Locked Out - Ground Lift Up Permanently Closed, Function Locked Out - Ground Rear Deck Ext Permanently Closed, Function Locked Out - Ground Rear Deck Ret Permanently Closed, Function Locked Out - Ground Start Switch Permanently Closed, Function Problems, Function Problems - Ground Control Box, Ground Front Deck Extend/Retract Active Together, Ground Lift Up/Down Active Together, Ground Rear Deck Extend/Retract Active Together, Indicates Difficulty with the Ground Controls - Function Problem - Brake Release Permanently Selected, Indicates Difficulty with the Ground Controls - Function Problem - Lift Permanently Selected, Indicates Difficulty with the Ground Controls - Ground Lift Up/Down Active Together, Indicates Difficulty with the Ground Controls - No Data From Tilt Sensor - Not Connected or Faulty, Indicates Difficulty with the Ground Controls - Tilt Sensor Not Calibrated, No Signal From Tilt Sensor X Axis - Check Wiring, No Signal From Tilt Sensor Y Axis - Check Wiring, Not Used, Over Maximum Throttle, Problems with Ground Controls
Level Sensor Failure · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Fault code 23 on JLG scissor lifts (M3369, M4069) covers a group of ground control faults: switches stuck closed at power-up, lift up/down active together, or tilt sensor signal loss/miscalibration. It locks out the affected function until the switch is released or the wiring/sensor issue is fixed. No single numeric threshold applies to all variants, but the tilt sensor dropout timing and assumed tilt angle are specified.
Medium severity. The machine is not in immediate danger, but functions are locked out for safety until the fault clears. If the tilt sensor fault is active, the controller assumes a worst-case slope and slows or limits drive, which affects normal operation and should be resolved before continued use.
What does JLG Scissor Lift error code 23 mean?
Fault code 23 is actually a family of related ground control faults grouped under one code on JLG scissor lifts. Most variants mean the controller saw a switch in the ground control box (lift up, lift down, start, glow plug, or deck extend/retract) closed at power-up, or saw two opposing functions (like lift up and lift down) active at the same time. In either case the controller locks out that function as a safety measure rather than guessing what the operator wants.
Other variants under this code relate to the tilt sensor inside the ground control box. If the controller stops seeing valid transitions on the tilt X or tilt Y signal, or if the tilt sensor's calibration memory still holds the factory test signature instead of a real calibration, the system assumes the machine is tilted to a worst-case slope angle. This causes drive to be limited or slowed in both directions as a precaution.
Because this code bundles several distinct problems, the fix depends entirely on which specific message the display shows: a stuck switch, two switches closed together, or a tilt sensor wiring/calibration issue.
What triggers a JLG Scissor Lift 23 code?
For the tilt sensor dropout: the fault sets if no transitions are detected on the tilt X or tilt Y signal for 2000 milliseconds, and it is retained until transitions are sensed on both signals again. When active, the controller assumes the vehicle is tilted to +20.0 degrees on the X axis and +20.0 degrees on the Y axis, which limits stowed drive demand as in a worst-case slope descent, in both forward and reverse. For the lift up/down or switch-closed variants, the fault sets when the respective digital input is energized at power-up or when opposing lift inputs are energized simultaneously, and it is retained until the input(s) are momentarily de-energized.
Common causes of 23
- Lift switch (up or down) in the ground control box was closed or stuck at start-up, energizing the lift up or lift down digital input during power-up.
- Start switch in the ground control box was closed at start-up.
- Glow plug switch in the ground control box was closed at start-up.
- Ground lift up and ground lift down digital inputs energized simultaneously, which the control system reads as both directions active together.
- No signal from the tilt sensor mounted inside the ground control box, caused by a wiring or connector problem at the sensor or at the ground control board.
- Tilt sensor's calibration EEPROM still holds the signature written by the in-circuit test fixture rather than a valid field calibration.
- Similar switch-closed-at-startup and simultaneous-activation conditions on front deck extend/retract, rear deck extend/retract, and auxiliary ground switches.
How to troubleshoot JLG Scissor Lift 23: first checks
- Check every switch in the ground control box (lift up/down, start, glow plug, deck extend/retract, aux) for a stuck or physically jammed position before powering up again.
- Cycle the affected switch to the neutral/off position; most switch-closed lockouts clear once the switch is released.
- Inspect wiring and plug connections at the tilt sensor and at the ground control board for looseness, corrosion, or damage if the message points to a tilt sensor signal loss.
- Check the lift switch and its associated wiring in the ground control box if the fault indicates lift up and down are active together.
- Confirm whether the tilt sensor has ever been through the field calibration procedure; a machine fresh from the test fixture will still show the factory signature until calibrated.
- Look for pinched or chafed harness sections near the ground control box, since intermittent switch or sensor faults often trace back to harness damage in that area.
How the code clears
Clearing depends on which specific condition triggered code 23. For a switch stuck closed at power-up, release or repair the switch to clear the message. For lift up/down active together, check the lift switch and wiring, then momentarily de-energize both inputs. For tilt sensor signal loss, check and repair wiring and plug connections at the tilt sensor and the ground control board; the fault clears once transitions are sensed again on both tilt axes. For an uncalibrated tilt sensor, run the calibration procedure to overwrite the test-fixture signature with a valid calibration; no other reset step is listed.
Affected models and serial ranges
23 appears in our records across 2 JLG Scissor Lift models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| M3369 | Serial range not listed in source records |
| M4069 | Serial range not listed in source records |
Frequently asked questions
What does JLG fault code 23 mean on a scissor lift?
It is a grouped code covering several ground control problems: a switch stuck closed at power-up, lift up and down active together, or a tilt sensor signal or calibration problem. The exact cause shows in the help message text on the display.
Why is my scissor lift's drive slow or limited with code 23 active?
If the fault is tied to the tilt sensor, the controller assumes the machine is tilted to a worst-case angle (+20.0 degrees on both X and Y axes) and limits stowed drive demand in both forward and reverse as a safety precaution, resulting in slow forward drive.
How do I clear a lift permanently selected fault?
Release the lift switch (up or down) in the ground control box. If releasing it does not clear the fault, inspect the switch and wiring for damage causing it to stick closed.
My tilt sensor fault won't clear, what should I check?
Check wiring and plug connections at the tilt sensor and at the ground control board. The fault is retained until valid transitions are sensed again on both the tilt X and tilt Y signals for the required period.
Does code 23 require recalibrating the tilt sensor?
Only if the specific message indicates the calibration EEPROM still holds the in-circuit test fixture signature. In that case, run the tilt sensor calibration procedure; a wiring check will not resolve this variant.
Is it safe to keep operating with fault code 23 showing?
The controller has already locked out the affected function or limited drive as a precaution, so the machine is protecting itself. Continuing to operate with a function locked out is not productive and the underlying switch or sensor issue should be fixed before returning to normal work.
Which JLG models does this fault code apply to?
This fault code and its associated ground control messages apply to JLG scissor lift models M3369 and M4069.