JLG Telescopic Boom Lift 14 Fault Code: Manifold Absolute Pressure (MAP) Low Voltage
Also called Chassis Tilt Sensor Out of Range, Help Comment - Chassis Tilt Sensor Out of Range, Overcrank, Overcrank - 3 Failed Crank Cycles, Underspeed, Underspeed - Below 2000 RPM
Manifold Absolute Pressure (MAP) Low Voltage · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Fault code 14 on JLG telescopic boom lifts (E600 platform) covers several different conditions depending on system: chassis tilt sensor detecting the machine tilted beyond 19 degrees for more than 4 seconds, engine overcrank after 3 failed crank cycles, engine underspeed below 2000 RPM, or a low voltage signal from the Manifold Absolute Pressure (MAP) sensor. The chassis tilt version triggers a shutdown (RBS condition) and is not reported during power-up.
High severity. A tilt-related code 14 shuts the machine down (RBS condition) because operating on an out-of-level chassis risks tip-over. Overcrank and underspeed codes point to engine start or run problems that can leave the machine disabled in the field. None of these should be worked around; diagnose before returning to service.
What does JLG Telescopic Boom Lift error code 14 mean?
Fault code 14 is used across several JLG telescopic boom lift systems, so the meaning depends on which description accompanies it. On the chassis leveling system, it means the chassis tilt sensor has reported the machine tilted more than 19 degrees for longer than 4 seconds. This is the condition most tied directly to safe boom operation, since operating an elevated platform on an out-of-level chassis increases tip-over risk.
On the engine control side, the same code number can represent an overcrank condition, meaning the starter cranked the engine through 3 failed crank cycles without a successful start, or an underspeed condition, meaning engine speed dropped below 2000 RPM during operation. A separate variant flags low voltage from the Manifold Absolute Pressure (MAP) sensor circuit.
The chassis tilt version of this fault is not reported during the power-up sequence. It becomes active only after a time delay bypass period has elapsed following engine startup, and when active it forces a shutdown response (RBS condition).
What triggers a JLG Telescopic Boom Lift 14 code?
For the chassis tilt sensor version: the controller sets the fault when tilt angle exceeds 19 degrees for more than 4 seconds, and this check is not active during power-up but becomes enabled once the time delay bypass period has elapsed after engine startup. For overcrank: the fault sets after 3 failed crank cycles. For underspeed: the fault sets when engine speed falls below 2000 RPM.
Common causes of 14
- Machine parked or operated on uneven, sloped, or soft ground causing the chassis to tilt beyond the allowed angle
- Faulty or misaligned chassis tilt sensor giving a false out-of-range reading
- Low fuel level or poor fuel connections preventing normal engine start (relevant to overcrank/underspeed variants)
- Fuel solenoid or fuel pump not operating correctly
- Low start battery voltage insufficient to crank or sustain engine speed
- Inadequate combustion air supply, such as a blocked air cleaner
- Governor lever out of adjustment, affecting engine speed control
- Cold ambient temperature with a non-functioning heater or glow plug preventing normal ignition
- Low voltage condition on the MAP sensor circuit
How to troubleshoot JLG Telescopic Boom Lift 14: first checks
- Check where the machine is parked or positioned; move it to level, stable ground and see if the fault clears
- Inspect the chassis tilt sensor and its wiring for damage, corrosion, or looseness
- Check fuel level and all fuel line connections for leaks or blockage
- Verify operation of the fuel solenoid and fuel pump
- Check start battery voltage
- Look at exhaust while attempting to start: white smoke suggests fuel is reaching the engine but not igniting, which points toward ignition or OEM-level engine checks
- In cold weather, confirm the heater and/or glow plug are functioning
- Check the air cleaner and air intake path for restrictions
- Verify the governor lever setting and readjust if it has drifted out of specification
How the code clears
No separate clearing step is listed beyond correcting the underlying condition. For the chassis tilt version, leveling the machine and waiting past the time delay bypass period after engine startup should allow normal operation to resume once the chassis is within the allowed angle. For engine-related versions (overcrank, underspeed, MAP low voltage), resolving the fuel, air, battery, or governor issue identified in the checks is expected to clear the fault on the next start attempt. No reset procedure beyond these corrective actions is listed.
Affected models and serial ranges
14 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 14 mean on a JLG boom lift?
It depends on the system reporting it. Most often on telescopic boom lifts it points to the chassis tilt sensor detecting the machine tilted more than 19 degrees for over 4 seconds, which forces a shutdown. On the E600 engine platform, the same code number can also mean overcrank (3 failed crank cycles), underspeed (below 2000 RPM), or a MAP sensor low voltage condition.
Why does my JLG boom lift shut down with code 14 even on ground that looks flat?
The chassis tilt sensor can trigger from ground that looks flat but has a slope, dip, or soft spot under one set of wheels or outriggers. A faulty or misaligned sensor can also cause a false reading, so if the ground is genuinely level, have the sensor and its wiring checked.
Is code 14 reported when I first start the machine?
No. The chassis tilt check is not reported during power-up. It only becomes active once the time delay bypass period has elapsed after engine startup.
Can I keep operating the boom lift after code 14 appears?
No. This fault produces a shutdown response (RBS condition) for the chassis tilt version. Treat it as a stop-work condition until the machine is releveled or the underlying engine issue is diagnosed and fixed.
My engine won't start and shows an overcrank-type code 14. What should I check first?
Check fuel level and fuel connections, verify the fuel solenoid and fuel pump are working, and check start battery voltage. If exhaust shows white smoke during cranking, fuel is reaching the engine but it isn't firing, which points to further OEM-level checks. In cold weather, also confirm the heater and glow plug are operating.
What causes an underspeed code 14 on the engine?
Underspeed is set when engine speed drops below 2000 RPM. Causes include inadequate fuel or combustion air supply, a blocked air cleaner, or the governor lever being out of adjustment.
Does code 14 always require a dealer visit?
Not necessarily. Many causes, like repositioning the machine on level ground, checking fuel connections, or clearing an air cleaner restriction, are things an owner-operator can check directly. If those checks don't resolve it, especially on the engine-related variants, refer to OEM documentation for deeper diagnostics.