JLG Articulating Boom Lift 44 Fault Code: Problems with the Battery Supply
Also called Battery Low, Battery Too High - System Shut Down, Battery Too Low - System Shut Down, Coolant Level Switch Off, Heated Oxygen Sensor (HEGO2) High Voltage, Problems with the Engine
Problems with the Battery Supply · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Fault code 44 on a JLG articulating boom lift flags a battery supply voltage problem read by the engine or vehicle controller (SPN 111 / FMI 1). Depending on the control module, it can be a low-voltage warning that lets the machine keep running, or a too-high or too-low condition that forces a system shutdown requiring an EMS recycle (cycle the key or emergency stop off and on).
High severity. A simple low-battery warning is not an emergency, but a battery-too-high or battery-too-low shutdown stops the machine dead and points to a charging or wiring problem that needs prompt attention before further operation.
What does JLG Articulating Boom Lift error code 44 mean?
Fault code 44 is a battery/system voltage fault reported under SPN 111, FMI 1. It covers a family of related conditions, all tied to the machine's main battery or system supply voltage falling outside the range the controller expects. JLG lists several descriptions under this one code: Battery Low, Battery Too High - System Shut Down, Battery Too Low - System Shut Down, along with related text about coolant level switch, oxygen sensor voltage, and general battery supply or engine problems.
The core issue in nearly every variant is the same: the controller is watching battery voltage (or, on some platforms, a specific system voltage) and comparing it against low and high thresholds. If voltage drifts too low, it is treated as a warning at first, then a shutdown-level fault if it drops further. If voltage climbs too high, that is also treated as a shutdown-level fault.
Exact thresholds differ depending on which controller and platform generated the fault, since JLG documents several slightly different voltage windows across different control modules. In every case, a shutdown-level fault requires an EMS recycle (turning the emergency stop or key off and back on) before the machine will run again.
What triggers a JLG Articulating Boom Lift 44 code?
JLG documents several distinct voltage thresholds depending on the specific controller reporting the fault. Battery low warnings are set when battery voltage drops below 11 volts (on some controllers, only if this persists for more than 5 seconds, and it is not detected during engine crank). Battery too high shutdown is set when voltage rises above 16 volts or, on another controller variant, above 18 volts. Battery too low shutdown is set when voltage falls below 9 volts, or on another variant below 6 volts. Two additional descriptions reference system volts low below 9 volts and system volts high above 16 volts. On a higher-voltage platform, the same fault family triggers battery low below 40 volts, battery too high shutdown above 62 volts, and battery too low shutdown below 33 volts.
Common causes of 44
- Weak, undercharged, or failing main battery that cannot hold voltage under load
- Charging system problem, such as a faulty alternator or voltage regulator, allowing voltage to climb too high or sag too low
- Loose, corroded, or damaged battery terminals or main power wiring causing voltage drop or an unstable reading at the controller
- Bad ground connection between the battery, engine, and chassis
- Faulty or failing engine control module (ECM) power supply circuit or related wiring harness
- Related sensor or switch issues referenced alongside this code, including coolant level switch and heated oxygen sensor (HEGO2) circuit problems, which can appear in the same diagnostic grouping on some engine platforms
How to troubleshoot JLG Articulating Boom Lift 44: first checks
- Check battery voltage at rest and under load with a multimeter, and compare the reading against the low and high thresholds listed for your controller
- Inspect battery terminals, main power cables, and ground straps for corrosion, looseness, or damage, and clean or tighten as needed
- Start the engine and check charging voltage to confirm the alternator or charging system is holding voltage in a normal range and not drifting toward the high or low shutdown thresholds
- Check wiring harness connectors at the controller and engine control module for corrosion, pin damage, or loose pins
- Verify the coolant level switch and any related sensors mentioned in this fault group are connected and functioning, since these can be reported under the same diagnostic code on certain engines
- Look at machine history for repeated low-battery warnings, which often precede a full shutdown fault as the battery or charging system continues to degrade
How the code clears
For the low-battery warning, no shutdown occurs and no separate clearing step is listed beyond correcting the underlying voltage issue. For the battery-too-high or battery-too-low shutdown conditions, JLG specifies an EMS recycle is required: cycle the emergency stop switch or key off and back on to clear the shutdown and attempt to restart. If the fault resets immediately or recurs, the underlying battery, charging, or wiring problem still needs to be fixed before continued operation.
Frequently asked questions
What does fault code 44 mean on a JLG boom lift?
It means the controller has detected the battery or system voltage outside its normal operating range. This can be a simple low-voltage warning or a full system shutdown if voltage is too high or too low, depending on which threshold was crossed.
Will the machine shut down with fault code 44?
Not always. A battery low warning below 11 volts is just a warning and the controller keeps running. But battery too high or battery too low conditions force a system shutdown that requires an EMS recycle before the machine will operate again.
How do I clear fault code 44 after a shutdown?
Cycle the emergency stop switch or key off and back on, which is the EMS recycle JLG specifies for the battery too high and battery too low shutdown conditions. If the fault returns right away, the voltage problem has not actually been fixed.
Why does the voltage threshold for this code seem different on different machines?
JLG uses different controllers and voltage systems across its boom lift lineup. Some report shutdown thresholds around 16 volts to 18 volts high and 6 volts to 9 volts low, while higher-voltage platforms use thresholds like 62 volts high and 33 volts low. Check which controller variant your machine uses before comparing readings.
Can a bad alternator cause fault code 44?
Yes. A charging system that overcharges or undercharges the battery can push system voltage above or below the thresholds that trigger this fault, so the alternator and voltage regulator should be checked as part of diagnosis.
Is fault code 44 related to the coolant level switch or oxygen sensor?
JLG groups some related descriptions, including coolant level switch off and heated oxygen sensor (HEGO2) high voltage, under the same SPN 111 / FMI 1 code on certain engine platforms. If you see this fault alongside coolant or emissions-related symptoms, check those circuits as well.
Does fault code 44 happen during engine cranking?
On some controllers, the battery low warning is specifically not detected during crank, since voltage naturally dips while the starter is engaged. The fault is meant to catch sustained low voltage during normal running, not the brief dip at startup.