JLG Scissor Lift 337 Fault Code: Crank Loss
Also called Steer Left Short to Battery
Crank Loss · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Code 337 on JLG scissor lifts means the ground board detected voltage on the steer left solenoid circuit while that solenoid was commanded off at power up. This points to a short to battery voltage in the wiring or solenoid circuit, identified as SPN 636 / FMI 4.
Medium severity. Steering function may be affected or disabled until this is diagnosed. It is not an immediate safety emergency, but the machine should not be relied on for normal steering operation until the circuit is checked and confirmed good.
What does JLG Scissor Lift error code 337 mean?
Fault code 337 is set when the ground board on a JLG scissor lift sees voltage present on the steer left solenoid circuit at power up, even though the controller has commanded that solenoid off. In a healthy system, an off solenoid circuit should read no voltage back to the ground board when it is not energized. Voltage showing up anyway tells the controller that the circuit is shorted to a source of battery voltage somewhere between the ground board and the solenoid.
This matters because the steer left solenoid is part of the hydraulic steering control system. If the ground board cannot trust the state of this circuit, it may restrict or disable steering functions as a protective measure, and an unexpected short to battery voltage can also point to chafed wiring, a failed solenoid coil, or an internal ground board fault that could cause other electrical problems if left unaddressed.
Common causes of 337
- A short to battery voltage somewhere in the steer left solenoid circuit wiring.
- Physical damage to the wiring harness between the ground board and the steer left solenoid, such as chafing or pinching that exposes bare wire to a voltage source.
- A failed steer left solenoid coil that does not match the expected resistance of about 30 ohms.
- A faulty ground board that is either generating a false signal internally or has a damaged output/input stage.
How to troubleshoot JLG Scissor Lift 337: first checks
- Check continuity through the steer left solenoid circuit and measure solenoid resistance, it should read about 30 ohms.
- Confirm the solenoid's power feed comes from ground board pin J1-21 at 24V, and that its ground path returns properly to ground board pins J1-30 and J1-37.
- Visually inspect all wiring in this circuit for physical damage, chafing, pinched insulation, or corrosion at connectors.
- If wiring and solenoid resistance check out normal, the ground board itself is the likely remaining cause and should be replaced.
How the code clears
No separate clearing step is listed for this code. Repair should focus on correcting the wiring fault, replacing the solenoid if it is out of spec, or replacing the ground board once the electrical short to battery voltage is resolved.
Frequently asked questions
What does JLG fault code 337 mean?
It means the ground board detected voltage on the steer left solenoid circuit while that solenoid was commanded off at power up, indicating a short to battery voltage in the circuit, identified as SPN 636 / FMI 4.
What is the resistance of the steer left solenoid on a JLG scissor lift?
The steer left solenoid should measure about 30 ohms. A reading well outside that suggests a bad coil.
Where does the steer left solenoid get its power and ground on a JLG scissor lift?
It is powered with 24V from ground board pin J1-21, with its ground returning to ground board pins J1-30 and J1-37.
Can I keep driving or steering the lift with code 337 active?
Steering control may be affected since the controller has flagged an unreliable circuit state. It is best to diagnose the fault before relying on normal steer function.
Is code 337 caused by a bad wire or a bad part?
It can be either. Common causes include physical wiring damage causing a short to battery voltage, a failed solenoid coil, or in some cases a faulty ground board if wiring and solenoid check out fine.
How do I fix JLG fault code 337?
Check continuity and resistance of the steer left solenoid circuit, inspect wiring for physical damage, and replace the ground board if the wiring and solenoid test normal.