609 609 105609 609 104

Faults and error codes · boom lift

JLG 600AJ service: faults and error codes

The most common faults of the JLG 600AJ (boom lift) with the likely cause and the way to diagnose them, and below the JLG error codes with explanations. RK Rental services the JLG 600AJ: repairs, maintenance inspections and preparation for UDT inspections (UDT is the Polish Office of Technical Inspection), parts and service life assessment.

The information below is diagnostic and indicative. Repairs, calibrations and clearing of fault codes are carried out by a qualified service technician, according to the manual for the specific serial number of the machine. A machine with an active fault code must not be used until the cause has been removed.

Most common JLG 600AJ faults

Boom will not raise or extend

Likely cause
Discharged battery, an active fault code, basket overload or a fault of the boom angle or length sensor.
Diagnosis / how to fix it
Check the power supply, read the fault code and verify the load in the basket.

Machine will not drive, or drives only at creep speed

Likely cause
Joystick out of range or not centred, an open footswitch, or the drive limitation that is active while the boom is raised.
Diagnosis / how to fix it
Centre the joystick, check the footswitch and lower the boom to the stowed (transport) position.

Tilt alarm

Likely cause
Working on a slope, or a damaged or uncalibrated tilt sensor.
Diagnosis / how to fix it
Level the machine; calibration or replacement of the sensor at a service centre.

Basket overload (overload / load sense)

Likely cause
Capacity exceeded or a basket load sensor out of calibration.
Diagnosis / how to fix it
Reduce the load; calibration of the weighing system at a service centre.

Boom sagging or descending slowly

Likely cause
Worn cylinder seals, a holding valve fault or air in the system; moisture can make valves stick.
Diagnosis / how to fix it
Inspect the cylinders, valves and hydraulic oil; repair at a service centre.

Loss of CAN communication between modules

Likely cause
Chafed bus cable, corroded connectors or a damaged module (basket, chassis, power module).
Diagnosis / how to fix it
Check the bus and the connectors and read the fault code with a service analyser.

Combustion engine: will not start, stalls, overheats

Likely cause
Glow plugs or relay, throttle position sensor (TPS), temperature and oil pressure sensors, fuel system.
Diagnosis / how to fix it
Read the engine codes and check the sensors and wiring.

Basket will not come down

Likely cause
No power to the lowering valves or an electrical fault.
Diagnosis / how to fix it
Use the emergency lowering (the valve on the chassis), then have the electrics diagnosed at a service centre.

JLG 600AJ error codes: 306 codes explained

JLG uses the JLG Control System. The flash code has the format group/subgroup (e.g. 2/1), and the full DTC is 3 to 5 digits (e.g. 255, 437, 662), read with a JLG analyser. The first digit indicates the system the fault relates to.

Below you see the code and the original manufacturer's message. Open a code for the likely cause, what you can check yourself and when to call service.

Source: JLG Service and Maintenance Manual: 600AJ (3121201), 800AJ (3120858), 460SJ, 860SJ, 1250AJP (3122581800), M450AJ (3121829), M600JP (3121711): Diagnostic Trouble Codes tables.

All JLG codes of this control system: list and search →

Do you have a fault or an error code on your JLG 600AJ?

Our service team will read the code, diagnose the cause and remove the fault, at our workshop or on site at the customer's premises (construction site, hall, warehouse), with original or OEM-grade replacement parts.

Book a service
← Back to JLG service

Contact

The fastest way is by phone: service +48 609 609 105 (also WhatsApp), or write to serwis@fajnepodnosniki.pl.

Phone (service):
+48 609 609 105
E-mail:
serwis@fajnepodnosniki.pl
WhatsApp:
+48 609 609 105
Base and office:
ul. Brzozowa 12, 86-061 Brzoza near Bydgoszcz, Poland
Office hours:
Monday to Friday, 7:30–15:30 (Polish time)
Response time:
Messages: a reply within 1–2 hours.