JLG 1200SJP: 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: Check the power supply, read the fault code and verify the load in the basket.

JLG 1200SJP: 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: Centre the joystick, check the footswitch and lower the boom to the stowed (transport) position.

JLG 1200SJP: Tilt alarm

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

JLG 1200SJP: Basket overload (overload / load sense)

Likely cause: Capacity exceeded or a basket load sensor out of calibration. Diagnosis: Reduce the load; calibration of the weighing system at a service centre.

JLG 1200SJP: 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: Inspect the cylinders, valves and hydraulic oil; repair at a service centre.

JLG 1200SJP: Loss of CAN communication between modules

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

JLG 1200SJP: 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: Read the engine codes and check the sensors and wiring.

JLG 1200SJP: Basket will not come down

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

Faults and error codes · boom lift

JLG 1200SJP service: faults and error codes

The most common faults of the JLG 1200SJP (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 1200SJP: repairs, maintenance inspections and preparation for UDT inspections (UDT is the Polish Office of Technical Inspection), parts and service life assessment.

JLG 1200SJP: machine data

Type: boom lift
Working height: 38.73 m
Platform capacity: 454 kg
Drive: Diesel

1200SJP machine card →1200SJP manuals and parts catalogue →JLG parts →

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.

JLG 1200SJP technical data useful for service

Weight and dimensions decide how the machine is transported to a workshop, while the tyres, battery and drive decide which parts are needed. When you report a service job, please also give the serial number from the rating plate.

Platform height: 36.73 m
Outreach: 22.86 m
Machine weight: 18,650 kg
Platform dimensions: 2.44 × 0.91 m
Transport dimensions (L × W × H): 10.64 × 2.49 × 3.04 m
Drive: 4WD
Use: Outdoor
Number of persons: 2
Platform Height-Raised: 36.73 m
Platform Capacity (restricted): 454 kg
Platform Capacity (unrestricted): 227 kg
Gradeability: 45%
Turning Radius-Inside: 2.44 m
Turning Radius-Outside: 5.89 m
Fuel Tank Capacity: 117 L

Most common JLG 1200SJP 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 error 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.

Code	Meaning
Group 2	Panels and controls (key switch, joystick, switches).
Group 3	Line contactor and control outputs (valves, coils).
Group 4	Thermal and power supply (power module overheating, battery voltage, engine code).
Group 6	CAN communication and modules.
Group 8	Tilt sensor and platform load sensing system.
211	POWER CYCLE: a normal message at start-up.
212	Platform and ground mode selected at the same time (faulty key switch).
226	Joystick out of the 0.5–4.5 V range or not centred.
255	PLATFORM OVERLOADED: platform overload.
256	Pothole protection did not deploy.
421	Power module overheated (PLEASE WAIT message).
437	ENGINE TROUBLE CODE: an engine fault has been detected (see the code from the ECU).
441	Battery voltage too low.
2/1	FWS FAULTY: inconsistent footswitch signals (EMS reset required).
661 / 662	Loss of CAN communication with the power module / the platform module.
811	Tilt sensor not calibrated.

Engine codes (at 437) come from a separate ECU (Deutz/GM) and depend on the power unit. A full diagnosis needs a JLG analyser: our service team will read the code and remove the fault.

Check any JLG code in our error code database →

Do you have a fault or an error code on your JLG 1200SJP?

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.

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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.