JLG Telescopic Boom Lift 44 Fault Code: Problems with the Battery Supply
Also called Coolant Level Switch Off, Problems with the Engine
Problems with the Battery Supply · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Fault code 44 (SPN 111 / FMI 1) on JLG telescopic boom lifts covers two different problems depending on the machine's control system: a low coolant level switch input, or a battery voltage supply fault (low, too high, or too low with system shutdown). Check which condition applies to your machine before diagnosing.
High severity. Some versions of this fault are warnings only and do not shut the machine down, but others trigger a full system shutdown requiring an EMS recycle, and the coolant-level variant triggers an emergency stop and start lock. Treat any code 44 as worth stopping to check before continuing operation.
What does JLG Telescopic Boom Lift error code 44 mean?
Fault code 44 is used across different JLG control systems for two distinct issues, so what it means on your machine depends on which body of diagnostic text applies. In most versions it is a battery supply voltage fault: the controller is watching battery voltage and flags a warning if it drops too low, or forces a shutdown if voltage goes too high or drops critically low.
In another version, the same code number is tied to a low coolant level switch being active. This is a functional fault that JLG classifies as switch-off, meaning it triggers an emergency stop and a start lock, preventing the machine from being started until the condition is cleared.
Because the description and severity differ so much between these variants (a voltage warning versus an engine coolant safety shutdown), the first step in diagnosing code 44 is confirming which fault text your analyzer or display is actually showing.
What triggers a JLG Telescopic Boom Lift 44 code?
For the battery supply variants, thresholds differ by control system: battery low (warning only, no shutdown) can be below 11 volts for more than 5 seconds, or simply below 11 volts on other systems, or below 40 volts on a higher-voltage system. Battery too high with system shutdown is above 16 volts, 18 volts, or 62 volts depending on the system, and requires an EMS recycle. Battery too low with system shutdown is below 9 volts, 6 volts, or 33 volts depending on the system, also requiring an EMS recycle on some versions. The low-battery warning is not detected during crank. For the coolant variant, the fault sets when the low coolant level switch input becomes active, with no separate voltage or time threshold given.
Common causes of 44
- Battery voltage has dropped below the low-voltage warning threshold for the control system in use, often due to a weak, aging, or undercharged battery
- Battery voltage has spiked above the high-voltage shutdown threshold, which can point to a charging system or alternator regulation problem
- Battery voltage has collapsed below the low-voltage shutdown threshold, indicating a severely discharged or failing battery, loose connection, or wiring fault
- Low coolant level switch input is active because coolant level in the reservoir or radiator has actually dropped
- Coolant level sensor or its cable has failed or is reading incorrectly even though coolant level itself may be fine
How to troubleshoot JLG Telescopic Boom Lift 44: first checks
- Identify which code 44 fault text is displayed (battery low, battery too high, battery too low, or low coolant level switch) since the correct fix depends on which condition triggered it
- Check the coolant level visually in the reservoir or radiator, topping off if low and watching for signs of a leak
- Inspect the coolant level sensor and its cable connector for damage, corrosion, or a loose pin
- Check battery voltage at rest and while running to see if it falls into any of the low or high thresholds listed for your control system
- Inspect battery terminals, ground connections, and charging system wiring for corrosion, looseness, or damage
- Check the alternator or charging system output if battery voltage is reading above the high-voltage threshold
How the code clears
For the battery-related versions, a battery too high or battery too low shutdown requires an EMS recycle before the machine will run again. The battery low warning does not shut the controller down and should clear on its own once voltage recovers. For the coolant level switch version, no separate reset procedure is listed beyond correcting the coolant level and switch condition, since the fault clears when the switch input is no longer active and the emergency stop and start lock are released.
Affected models and serial ranges
44 appears in our records across 1 JLG Telescopic Boom Lift models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| E600 | Serial range not listed in source records |
Frequently asked questions
What does fault code 44 mean on a JLG boom lift?
It depends on your control system. On most JLG telescopic boom lifts, code 44 (SPN 111 / FMI 1) is a battery voltage supply fault covering low, too high, or too low battery conditions. On another version, code 44 means the low coolant level switch input is active, which triggers an emergency stop and start lock.
Will fault code 44 shut down my JLG machine?
A battery low warning does not shut the controller down. However, battery too high or battery too low conditions do trigger a full system shutdown and require an EMS recycle. The coolant level switch version also stops the machine through an emergency stop and start lock.
What is an EMS recycle and when is it needed?
An EMS recycle is required after a battery too high or battery too low shutdown fault on the affected control systems. It essentially means cycling the engine management system, typically by turning the key or power off and back on, to clear the shutdown condition once battery voltage returns to normal.
How do I check the coolant level switch if I'm getting a low coolant fault?
Start by checking the actual coolant level in the reservoir or radiator. If the level looks fine but the fault persists, inspect the coolant level sensor itself and its cable connector for damage or a bad connection, since a faulty sensor can trigger the fault even with adequate coolant.
Why does my battery voltage keep tripping fault code 44?
Repeated low or high battery voltage faults usually point to a weak or failing battery, corroded or loose battery terminals, a charging system problem such as a bad alternator, or wiring issues in the battery supply circuit. Voltage thresholds vary by control system, so check what applies to your machine.
Is fault code 44 the same on every JLG telescopic boom lift?
No, this needs correction