JLG Articulating Boom Lift 815 Fault Code: Chassis Tilt Sensor Disagreement
Chassis Tilt Sensor Disagreement · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Fault 815 means the ground module found the two chassis tilt sensors on the ground board disagreeing with each other beyond allowed limits. When active, the ground module reports a faulted chassis tilt angle of 90°, which effectively tells the machine it is at maximum tilt regardless of actual position.
High severity. A faulted 90° tilt reading will likely cut or restrict drive, steer, and boom functions as a safety precaution, since the machine cannot trust its actual slope. Treat this as a stop-and-diagnose condition before resuming operation.
What does JLG Articulating Boom Lift error code 815 mean?
Fault 815 is logged by the ground module when the two chassis tilt sensors mounted on the ground board do not agree closely enough with each other on either the X axis or the Y axis. Tilt sensors are what let the machine know if it is sitting level or on a slope, which is critical for safe boom extension and drive operation on articulating boom lifts.
This code will not be reported if DTC814 is already active, meaning 814 takes priority in the fault logic.
When fault 815 sets, the ground module does not just flag an error, it reports a faulted chassis tilt angle of 90°. This is a fail-safe value meant to represent worst-case tilt, which will likely restrict or block functions until the fault is cleared and resolved.
What triggers a JLG Articulating Boom Lift 815 code?
The ground module uses two different thresholds depending on machine activity. Condition 1: if a drive, steer, or boom function is active, or the engine is cranking, or the primary raw tilt sensor reading is greater than ±10°, then the fault sets if the two ground board tilt sensors disagree by 3° or more on either the X or Y axis for longer than 5 seconds. Condition 2: if no drive, steer, or boom function is active, the engine is not cranking, and the primary raw tilt sensor reading is less than ±10°, then the fault sets if the two tilt sensors disagree by 1° or more on either axis for longer than 3 seconds.
Common causes of 815
- Disagreement between the two ground board tilt sensors exceeding the allowed threshold for the given operating condition (active function/cranking/high tilt versus idle/low tilt state).
- A failing or drifting tilt sensor on the ground board that no longer reads accurately compared to its counterpart.
- Wiring or connector issues at the ground board tilt sensors causing erratic or inconsistent readings between the two sensors.
- Physical misalignment or mounting issue with one of the tilt sensors, causing a persistent offset between the two readings.
How to troubleshoot JLG Articulating Boom Lift 815: first checks
- Check for DTC814 first, since fault 815 will not be reported if 814 is active. Resolve 814 before troubleshooting 815.
- Inspect the ground board tilt sensor connectors and wiring for corrosion, looseness, or damage.
- Verify both ground board tilt sensors are securely mounted and not physically shifted or damaged.
- Compare the two tilt sensor readings against each other and against the primary raw tilt sensor to see how far apart they are and under what conditions (machine idle versus function active).
- Check machine orientation and confirm the chassis is actually near level during testing, since real tilt situations can also produce large disagreements if one sensor is faulty.
How the code clears
Cycle power to clear the fault. No separate clearing step is listed beyond a power cycle, so after addressing the sensor disagreement, turn the machine off and back on to reset the fault.
Frequently asked questions
What does JLG fault code 815 mean?
It means the ground module detected that the two chassis tilt sensors on the ground board disagree with each other by more than the allowed amount for the current operating condition, either 3° for 5 seconds during active functions or high tilt, or 1° for 3 seconds when idle and near level.
Why does the machine restrict movement when fault 815 is active?
Because the ground module reports a faulted chassis tilt angle of 90° when this fault is present. That fail-safe reading tells the control system to treat the machine as if it is at extreme tilt, which will likely limit or block drive, steer, and boom functions until the issue is resolved.
Why does fault 815 not show up sometimes even when sensors disagree?
If DTC814 is already active, fault 815 will not be reported. Always check for 814 first.
How do I clear fault code 815 on a JLG boom lift?
Cycle power to the machine. No other clearing procedure is listed. If the underlying sensor disagreement is not fixed, the fault will likely return.
Does fault 815 mean I have a bad tilt sensor?
It means the two ground board tilt sensors are not agreeing within the allowed limits. This can be caused by a failing sensor, wiring or connector problems, or a mounting issue, so each of these should be checked rather than assuming which sensor is at fault.
Is it safe to keep operating the lift with fault 815 active?
No. Since the control system responds by reporting a faulted 90° tilt angle, function movement will likely be restricted, and more importantly the machine cannot verify its actual slope, which is a core safety input for boom lifts. Stop and diagnose the tilt sensor disagreement before resuming operation.