JLG Scissor Lift 33 Fault Code: Contactor Coil is Short-Circuit
Also called Engine Coolant Temperature (EOT) Sensor High Voltage, Indicates an Output Driver Problem - Brake Open Circuit, Indicates an Output Driver Problem - Brake Short to Battery, Indicates an Output Driver Problem - Ground Alarm Short to Battery, Indicates an Output Driver Problem - Ground Overload Lamp Open Circuit, Indicates an Output Driver Problem - Ground Overload Lamp Short to Battery, Indicates an Output Driver Problem - Left Brake Open Circuit, Indicates an Output Driver Problem - Left Brake Short to Battery, Indicates an Output Driver Problem - Lift Dn Open Circuit, Indicates an Output Driver Problem - Lift Dn Short to Battery, Indicates an Output Driver Problem - Lift Up Open Circuit, Indicates an Output Driver Problem - Lift Up Short to Battery, Indicates an Output Driver Problem - Right Brake Open Circuit, Indicates an Output Driver Problem - Right Brake Short to Battery, Indicates an Output Driver Problem - Steer Left Open Circuit, Indicates an Output Driver Problem - Steer Left Short to Battery, Indicates an Output Driver Problem - Steer Right Open Circuit, Indicates an Output Driver Problem - Steer Right Short to Battery, Output
Contactor Coil is Short-Circuit · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Code 33 on a JLG scissor lift covers a group of output driver faults detected by the controller during power-up, including a short-circuited line contactor coil and several open circuit or short-to-battery conditions on brake, lift, steer, ground alarm, and overload lamp outputs. It is a controller self-check fault, not a single wire failure, and it blocks the related function until cleared.
High severity. Code 33 disables drive, steer, and lift functions tied to the failed output and can indicate a shorted contactor coil or a wiring fault. Machine should not be operated with this code active until the affected circuit is checked.
What does JLG Scissor Lift error code 33 mean?
Fault code 33 is a general output driver diagnostic code used by the JLG controller to flag a problem with one of several output circuits it checks during power-up. Depending on which output is affected, the description may reference the line contactor coil, brake circuits (left, right, or general), lift up or lift down solenoids, steer left or right solenoids, the ground alarm output, or the ground overload lamp output.
The controller runs a self-test on these outputs when the machine powers up. It checks whether voltage or current is present on a circuit when the driver for that circuit is commanded off, and whether current flows when the driver is commanded on. If the readings do not match what is expected, the controller logs an open circuit, a short to battery, or in the case of the line contactor, a short-circuited coil detected through over-current protection.
Because these are output driver checks, the underlying cause is almost always in the wiring, the coil, or the load device itself rather than in the controller logic. The fault is the controller's way of protecting itself and the machine from a damaged circuit by refusing to enable that output.
Common causes of 33
- Line contactor coil is short-circuited, so the contactor cannot energize when required and the controller's coil over-current protection trips.
- Valve or line contactor circuit is active (energized) when no driver circuit has been turned on, often caused by a wiring error to the valves or to the line contactor.
- Ground overload lamp circuit shows voltage present when the output driver was commanded off during power-up, with the load sensing system enabled.
- Ground overload input driven low and ground overload status detected low during power-up while machine setup has load set to CUTOUT PLT or CUTOUT ALL.
- Ground overload lamp circuit shows no current flow when current was expected during power-up (open circuit condition), with load sensing enabled.
- Ground alarm circuit shows voltage present when the output driver was commanded off during power-up, with the ground alarm function enabled.
- Ground alarm input driven low and ground alarm status detected low during power-up while machine setup has ground alarm set to DESCENT or MOTION.
- Lift up solenoid circuit shows voltage present when the output driver was commanded off during power-up (short to battery type condition).
- Lift up input driven low and lift up status detected low during power-up, which prevents drive, steer, and lift up until resolved.
- No motion interlocks are present for these output driver checks, meaning the fault is raised purely from the power-up self-test, not from an operator input.
How to troubleshoot JLG Scissor Lift 33: first checks
- Identify exactly which output driver variant is flagged (brake left/right, lift up/down, steer left/right, ground alarm, ground overload lamp, or line contactor) since the repair path differs for each.
- Inspect the wiring harness and connectors for the affected circuit for chafing, pinched wires, corrosion, or moisture that could cause a short to battery or an open circuit.
- Check the line contactor coil resistance and condition if the fault points to the contactor, since a shorted coil will trip the controller's over-current protection.
- Verify machine setup parameters for load cutout mode (CUTOUT PLT or CUTOUT ALL) and ground alarm mode (DESCENT or MOTION), since these settings affect which conditions trigger the fault.
- Check for wiring errors at the valve or line contactor connections, especially any crossed or miswired leads that could energize a circuit without a driver command.
- Confirm the ground overload lamp and ground alarm circuits have proper continuity and are not drawing or blocking current unexpectedly during power-up.
- Cycle machine power after inspection to see if the controller's power-up self-test clears once wiring or component issues are corrected.
How the code clears
No reset procedure is listed for this code. Since the fault is generated by a power-up self-test, correcting the wiring, coil, or component issue and then cycling machine power is the standard approach implied by how the check runs, but no separate clearing step is listed beyond fixing the underlying circuit.
Frequently asked questions
What does JLG fault code 33 mean on a scissor lift?
It means the controller's output driver self-test found a problem on one of several monitored circuits during power-up, such as the line contactor coil, a brake circuit, a lift or steer solenoid, the ground alarm, or the ground overload lamp. The exact description tells you which circuit is affected.
Can I still operate the lift with code 33 active?
No. The affected function, such as lift up, steer, or brake release, is prevented while this fault is active. It should be diagnosed and corrected before returning the machine to service.
Is code 33 always about the line contactor?
No. Code 33 covers many different output driver problems including brake open circuits, lift up or down short to battery, steer left or right faults, ground alarm faults, and ground overload lamp faults. The line contactor short-circuit is only one of the listed causes.
What is a short to battery condition in this context?
It means the controller detected voltage on an output circuit when it commanded that output's driver off. This usually points to a wiring fault where the circuit is shorted to a constant power source instead of being controlled properly by the driver.
Does machine setup affect whether code 33 triggers?
Yes, for the ground overload lamp and ground alarm variants. The fault depends on how the machine's load cutout mode (CUTOUT PLT or CUTOUT ALL) and ground alarm mode (DESCENT or MOTION) are configured.
Is there a reset procedure for code 33?
No reset procedure is listed for this code. Repairing the wiring, coil, or component causing the fault and cycling power is the implied approach, since the fault comes from a power-up self-test.
Why does code 33 block drive, steer, and lift at the same time?
When the lift up circuit variant is active, JLG's own description states drive, steer, and lift up are all prevented as a safety measure until the fault condition is cleared.