The JLG 400S telescopic boom lift features a comprehensive instrument cluster with warning indicators for safe operation. Understanding these lights is crucial for preventing downtime and ensuring operator safety on job sites.
JLG 400S Warning Light Symbols
| Symbol | Name | Color | What it means | What to do |
|---|---|---|---|---|
| Master Warning (Stop) | RED | A critical fault is detected, such as engine shutdown or hydraulic failure on the JLG 400S. | Stop machine immediately; refer to manual or contact service. | |
| Master Caution | AMBER | A non-critical issue needs attention, like a sensor fault or low fluid in the JLG 400S. | Check display messages and address soon. | |
| Check Engine | AMBER | The engine has a malfunction affecting emissions or performance on the JLG 400S. | Service engine; may reduce speed. | |
| Engine Oil Pressure | RED | Oil pressure is too low, risk of engine damage on the JLG 400S. | Stop engine; check oil level and pressure sensor. | |
| Battery / Charging | RED | Battery voltage is low or alternator not charging on the JLG 400S. | Check battery connections and alternator belt. | |
| Coolant Temperature | RED | Engine coolant is overheating on the JLG 400S. | Stop engine; check coolant level and radiator. | |
| Hydraulic System | AMBER | Hydraulic oil temperature or pressure is outside normal range on the JLG 400S. | Reduce load; check hydraulic oil level. | |
| Fasten Seat Belt | RED | Operator seat belt is not fastened on the JLG 400S. | Fasten seat belt to enable machine functions. | |
| Overload / Capacity | RED | Platform load exceeds rated capacity on the JLG 400S. | Remove excess load immediately. | |
| Mast / Lift Limit | AMBER | Boom or lift cylinder near mechanical limit on the JLG 400S. | Retract boom or lower platform. | |
| Reduced Power (Limp Mode) | AMBER | Engine power reduced to protect components on the JLG 400S. | Check for codes and service soon. | |
| Work Lights | GREEN | Auxiliary work lights are turned on for the JLG 400S. | No action needed. | |
| Beacon / Rotating Light | GREEN | Beacon is active indicating machine operation on the JLG 400S. | No action needed. | |
| Parking Brake | RED | Parking brake is engaged but machine motion is commanded on the JLG 400S. | Release parking brake before moving. | |
| Water in Fuel | AMBER | Water detected in diesel fuel system on the JLG 400S. | Drain water separator; service fuel filter. | |
| Air Filter | AMBER | Engine air filter restriction detected on the JLG 400S. | Replace air filter. | |
| Service / Hour Meter | AMBER | Scheduled maintenance interval reached on the JLG 400S. | Perform required service per manual. |
17 symbols shown. Icons follow ISO 2575 dashboard standards; exact graphics vary by model year.
Most Important Warning Lights
Overload Condition
Common causes
- Exceeding platform capacity
- Uneven load distribution
What to do
Immediately remove excess weight; the JLG 400S relies on load sensing to prevent tip-over.
Engine Overheating
Common causes
- Low coolant
- Clogged radiator
- Failed fan
What to do
Shut down engine, allow to cool; on JLG 400S, clean radiator fins and check coolant level.
Hydraulic System Failure
Common causes
- Low hydraulic oil
- Pump failure
- Blocked filter
What to do
Stop operation; check hydraulic oil level and condition; for JLG 400S, inspect for leaks near cylinders.
Hydraulic Oil Leak
Common causes
- Damaged hose
- Loose fitting
- Cylinder seal failure
What to do
Identify leak source; tighten fittings or replace hose; JLG 400S uses O-ring face seals.
Battery Discharge
Common causes
- Alternator failure
- Parasitic drain
- Old battery
What to do
Charge battery; test charging system; JLG 400S requires a fully charged battery for engine start.
Frequently Asked Questions
Why does my JLG 400S show a master warning with no display message?
Check the engine oil pressure and coolant temperature; a sensor fault may trigger the warning without a specific text.
Can I operate with the amber master caution light on?
Yes, but address the underlying issue soon; it may indicate a pending service or minor fault.
How do I reset the service hour meter light?
After performing maintenance, the light resets via the diagnostic menu; consult the JLG 400S manual for steps.
What does the overload light mean in motion?
It indicates the platform load is near or over capacity; the JLG 400S may limit functions to prevent tipping.
How often should I check hydraulic oil on the 400S?
Daily before use; the sight gauge on the reservoir shows level; use manufacturer-specified oil.
My battery light flickers at idle. Is it normal?
No; it indicates low voltage. Check alternator output; on the JLG 400S, the engine may need higher RPM to charge.