JLG Articulating Boom Lift 43 Fault Code: Problems with the Engine
Also called Air Filter Bypassed, Coolant Temperature Short to Ground, Engine Coolant Temperature (ECT) Sensor Low Voltage, Engine Trouble Code, Fuel Sensor Short to Battery, Fuel Sensor Short to Ground, High Engine Temperature, Low Oil Pressure, No Alternator Output, Oil Pressure Short to Battery, Oil Pressure Short to Ground, Throttle Actuator Failure, Wrong Engine Selected - ECM Present
Problems with the Engine · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Fault code 43 on JLG articulating boom lifts is a grouped engine fault covering multiple possible problems including high engine temperature, low oil pressure, no alternator output, air filter bypass, and coolant or fuel sensor wiring faults. The exact cause is identified by the specific description shown on the analyzer alongside code 43.
High severity. Several of the conditions grouped under code 43, especially high engine temperature and low oil pressure, can cause serious engine damage if the machine keeps running. Treat any code 43 as a stop-and-check situation until the specific cause is identified.
What does JLG Articulating Boom Lift error code 43 mean?
Code 43 is not a single fault, it is a bucket code that JLG uses to report a range of engine-related problems on articulated boom lifts. The analyzer will display code 43 along with one of the specific descriptions listed by the control system, such as 'High Engine Temp', 'No Alternator Output', 'Low Oil Pressure', 'Air Filter Bypassed', or a fuel or coolant sensor wiring fault.
This grouping exists because the JLG controller monitors engine health signals such as coolant temperature, oil pressure, alternator charging voltage, and sensor circuit voltages, and reports abnormal readings under this shared code number. On CANBUS-equipped machines with an engine ECM (Ford or Deutz depending on configuration), the ECM's own fault codes can also be passed through and reported as part of this same fault family.
Because code 43 covers everything from a clogged air filter to a shorted coolant sensor to an actual overheating or oil pressure emergency, the specific wording shown on the display or analyzer is critical. Always read the full fault description, not just the number 43, before deciding how urgent the repair is.
Common causes of 43
- High engine temperature: engine coolant temperature above 117°C on Ford-configured engines, or above 130°C on Deutz-configured engines
- Air filter bypassed: air filter is clogged, triggering the bypass valve or switch
- No alternator output: engine has been running for 15 seconds or more and battery voltage is still below 11.5 volts (one variant instead flags this when measured battery voltage is less than 12.5 VDC)
- Low oil pressure: on Deutz engines, oil pressure below 8 PSI after the engine has run for at least 10 seconds (one variant lists the same threshold as 0.5 BAR); on Ford engines, the Ford ECM itself reported a low oil pressure fault
- Oil pressure sensor short to battery: Deutz oil pressure sensor reading above 6.6 volts
- Oil pressure sensor short to ground: Deutz oil pressure sensor reading below 0.1 volts for more than 5 seconds (not checked during crank)
- Coolant temperature sensor short to ground: Deutz coolant temperature sensor reading below 0.1 volts
- Fuel sensor short to battery: fuel sensor reading above 4.3 volts
- Fuel sensor short to ground: fuel sensor reading below 0.2 volts
- Wrong engine selected, ECM present: a CANBUS ECM was detected even though the machine is configured for a non-CANBUS engine
- Throttle actuator failure (listed as one of the possible engine-related descriptions under this code)
- Passed-through engine ECM fault codes: on Ford-equipped machines, most Ford ECM fault codes are passed through and reported under this family; on J1939 CANBUS-equipped machines, faults are reported in SPN/FMI format where the SPN identifies the failed component and the FMI identifies the type of failure
How to troubleshoot JLG Articulating Boom Lift 43: first checks
- Read the exact fault description paired with code 43 on the analyzer or display, this tells you which of the listed conditions actually triggered it
- Check engine coolant temperature gauge or sensor reading and compare against the 117°C (Ford) or 130°C (Deutz) thresholds; if the engine is genuinely overheating, stop the engine and let it cool before continuing work
- Inspect the air filter for clogging or restriction if 'Air Filter Bypassed' is shown
- Check battery voltage and alternator output with the engine running for at least 15 seconds; if it stays below 11.5 volts (or below 12.5 VDC on some models), inspect alternator wiring, belt, and connections
- Check oil pressure against the 8 PSI (0.5 BAR) threshold if a low oil pressure fault is shown; do not continue operating with confirmed low oil pressure
- Inspect wiring and connectors at the oil pressure sensor, coolant temperature sensor, and fuel sensor for corrosion, chafing, or loose pins if a short-to-battery or short-to-ground fault is indicated
- If the machine uses a CANBUS-equipped engine ECM, check for a reported SPN/FMI code or a Ford ECM code passed through, and look up that specific code for the precise component and failure type
- Confirm the correct engine type is selected in the machine configuration if 'Wrong Engine Selected, ECM Present' is shown
How the code clears
No separate clearing step is listed for code 43 as a whole. Since it represents multiple distinct underlying faults, clearing depends on correcting the specific condition shown (for example, fixing a wiring short, restoring alternator output, or resolving an overheating condition) and then following the engine or ECM's own fault handling behavior. If the fault is tied to a pass-through engine ECM code, that code's own clearing conditions apply.
Frequently asked questions
What does JLG fault code 43 mean?
It is a general engine trouble code that JLG boom lifts use to report a range of engine-related problems, including high engine temperature, low oil pressure, no alternator output, a clogged air filter, or a shorted sensor circuit. The analyzer shows a specific description along with the number 43 that identifies the actual problem.
Is it safe to keep operating with fault code 43 displayed?
It depends on the specific description shown. If it indicates high engine temperature or low oil pressure, stop operating immediately since continuing can cause engine damage. If it indicates a less urgent issue like a clogged air filter, you can usually finish the task safely but should service it soon.
Why does my JLG boom lift show 'No Alternator Output' under code 43?
This is set when the engine has been running for 15 seconds or more and the battery voltage is still below 11.5 volts (or below 12.5 VDC on some configurations). Check the alternator, drive belt, and battery connections.
What oil pressure triggers the low oil pressure fault under code 43?
On Deutz-configured engines, the fault sets when oil pressure drops below 8 PSI (0.5 BAR) after the engine has run for at least 10 seconds. On Ford-configured engines, this fault instead comes directly from the Ford engine ECM.
Does code 43 always mean the same problem?
No. Code 43 is a shared code number covering many different engine-related descriptions, from a clogged air filter to a shorted coolant temperature sensor to an actual engine overheating condition. Always check the specific text paired with the code.
What temperature triggers the high engine temperature fault?
Above 117°C on Ford-configured engines and above 130°C (266°F) on Deutz-configured engines.
My machine shows an SPN/FMI code along with fault 43, what does that mean?
On machines with a J1939 CANBUS engine ECM, engine faults are reported in SPN/FMI format. The SPN number identifies which component or circuit is affected, and the FMI number describes the type of failure. Look up that specific SPN/FMI pair for detail beyond the general code 43 description.