Telehandler Load Moment Indicator (LMI) Warning or Boom Cut-Out: What It Means

What the LMI does

A load moment indicator watches how far the load is from the machine and warns the operator before the machine reaches its tipping point. Terex's Telelift workshop manual describes it as "an electronic device designed to help the operator in the current use of the machine, warning him of imminent dangerous conditions by means of visual and acoustic signals." When the limit is reached, the system stops the manoeuvre.

Why it trips

Most LMI warnings are correct: the load is heavier, or further out, than the load chart allows for that boom angle and extension. The other common cause is a wrong setting. Terex is explicit that the operator "is responsible for the correct setting of the machine load table" and that "an incorrect setting of the tables can cause an incorrect operation of the LMI and lead to a dangerous situation." The right table changes when attachments are fitted or removed (forks, jib, winch, basket), and with operating mode, such as on wheels or on outriggers. On the Telelift, outrigger and turret positions are read automatically by micro-switches, so a faulty switch can put the system in the wrong mode.

Check the LMI before you work

Terex requires the operator to confirm the LMI is working before starting: the displayed values should look right, there should be no messages or alarms showing, and the manoeuvre-stopping functions should work. The manual also notes that the LMI runs a fail-safe self-diagnosis; if it detects a fault in itself or its sensors, it puts the machine in a safe state and stops the manoeuvres. A cut-out with no heavy load on the forks is therefore worth investigating, not overriding.

The bypass key is not a fix

Many LMIs have a key that overrides the shutdown. Terex's rules for it are strict: in normal operation the key "must not be positioned to by-pass shutdown"; it is "forbidden to use the key to lift loads exceeding the load values allowed by the Manufacturer"; and only authorised personnel may use it, in an emergency or a malfunction. Bypassing the LMI to finish a lift removes the one system watching the machine's stability.

A note on codes

Fault codes are not shared between makers. Genie, JLG, Skyjack, MEC, Manitou and CAT each number their faults differently, and the same maker numbers them differently across control generations. The descriptions here explain the component and how it fails; the code your machine shows has to be looked up in that machine's own service manual, by model and serial number.

Frequently Asked Questions

Related Guides

• Boom Angle Sensor Fault on a Boom Lift or Telehandler: What It Means and What to Check Why a boom angle sensor fault slows or stops a boom lift or telehandler, what the controller is protecting against, and the checks and calibration that clear it.
• Boom Length or Extension Sensor Fault: Why the Boom Won't Extend and What to Check What a boom length (extension) sensor fault means on a boom lift or telehandler, why extend and lift functions stop, and the checks the manufacturers list.
• Outrigger or Stabilizer Fault: Why the Machine Won't Lift or Drive Why outriggers or stabilizers that are not confirmed in position stop a scissor lift or telehandler, and the limit switch and coil checks the manufacturers list.
• Tilt Alarm or Level Sensor Fault on a Scissor Lift, Boom Lift or Telehandler Why a tilt alarm sounds and lift and drive stop, how to tell a real slope from a sensor problem, and why installing and calibrating the level sensor correctly matters.