JLG Boom Lift 22 Fault Code: Engine Starting System Fault
Also called Engine Starting System Fault 4, Problems with Drive & Steer Selection
Engine Starting System Fault · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Code 22 on JLG boom lifts (M600) covers a group of related faults: engine starting system problems (start battery, magneto, or magneto-voltage regulator) and drive/steer selection interlock problems tied to the foot switch (FWS) and joysticks. It is an alarm condition, not a shutdown, but it should be checked before continuing operation.
Medium severity. Code 22 is flagged as an alarm, not a shutdown, so the machine keeps running. Still, it points to either a weak engine starting circuit or a foot switch/joystick interlock fault that affects safe drive and steer control, so it should be diagnosed before the shift continues.
What does JLG Boom Lift error code 22 mean?
Fault code 22 on JLG boom lifts groups together several distinct problems under one code: issues with the engine starting system (start battery, engine magneto, or magneto-voltage regulator) and separate issues with drive and steer function selection tied to the foot switch (FWS) interlock and the joysticks.
On the engine starting side, the code points to a weak or failed start battery, or a charging problem in the magneto system that keeps the battery from being maintained properly.
On the drive/steer side, the code covers joystick center-tap or wiper voltage readings that are out of range, drive or steer being selected before or during the foot switch closing, both steer switches reading active at once, or the foot switch staying closed for seven seconds with nothing selected. JLG notes this alarm is not a shutdown, meaning the machine keeps operating, but the underlying issue should still be corrected.
What triggers a JLG Boom Lift 22 code?
JLG lists these set conditions: drive joystick center tap out of valid range or wiper wire-off; drive selected before and during foot switch (EMS/FWS) closure; foot switch closed for 7 seconds with no function selected; steer selected before and during foot switch closure; both steer switches active together; foot switch closed when platform mode was selected; or more than one of the drive, lift, and swing joystick center tap or wiper voltages out of range at the same time.
Common causes of 22
- Failed or discharged engine start battery
- Problem with the engine start battery charging system (low or no current output)
- Fault in the engine magneto or magneto-voltage regulator
- Drive joystick center tap out of valid range or wiper wire-off
- Drive or steer selected before and during foot switch (EMS/FWS) closure
- Both steer switches active at the same time (stuck or shorted switch)
- Foot switch closed for seven seconds with no function selected, tripping the FWS interlock
- Foot switch closed when platform mode was selected, so the controller is waiting for FWS to open
- Short circuit across a joystick port causing multiple joystick center tap or wiper voltages to read out of range at once
How to troubleshoot JLG Boom Lift 22: first checks
- Check the engine start battery charging system for current output
- Inspect the engine start battery for signs of failure (weak charge, corrosion, damaged terminals) and test or replace as needed
- Check the drive joystick wiring and connectors for the center tap and wiper circuits, looking for loose, corroded, or wire-off conditions
- Check the platform box wiring for shorts across joystick ports if more than one joystick shows out-of-range voltage
- Inspect the foot switch (FWS) for proper operation, making sure it is not stuck closed and that it opens and closes cleanly
- Check both steer switches to confirm only one can be active at a time
How the code clears
No separate clearing procedure is listed for this code. Since JLG notes the alarm is not a shutdown, correcting the underlying starting system or interlock issue (battery, charging current, joystick wiring, or foot switch operation) should allow normal operation to resume. Always verify repairs by re-testing the affected function before returning the machine to service.
Affected models and serial ranges
22 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 22 mean?
It is a combined code covering engine starting system problems (start battery, magneto, or magneto-voltage regulator) and drive/steer selection interlock problems related to the foot switch and joysticks on JLG boom lifts, including the M600.
Is fault code 22 a shutdown code?
No. JLG describes this as an alarm condition, not a shutdown, so the machine continues to operate, but the cause should still be checked and corrected.
Why does the foot switch trigger code 22?
The foot switch (FWS) works as an interlock for drive and steer selection. Code 22 can be set if drive or steer is selected before or during foot switch closure, if the foot switch stays closed for seven seconds with nothing selected, or if it is closed when platform mode is selected.
Can a bad battery cause code 22?
Yes. JLG lists a failed engine start battery or a charging system that is not producing proper current output as causes tied to this code.
Why would both steer switches be active at once?
This points to a stuck, shorted, or miswired steer switch, since normally only one steer switch should be active at a time. JLG lists this as one of the direct causes of code 22.
What should I check first if I get code 22 on my JLG boom lift?
Start with the engine start battery and its charging system output, then check the drive joystick wiring, foot switch operation, and steer switches, since these are the specific causes JLG lists for this code.