JLG Scissor Lift 26 Fault Code: Rear Deck Extend Valve Open Circuit
Also called Front Deck Extend Valve Open Circuit, Front Deck Extend Valve Short to Battery, Front Deck Extend Valve Short to Ground, Front Deck Retract Valve Open Circuit, Front Deck Retract Valve Short to Battery, Front Deck Retract Valve Short to Ground, Front Left Leveling Jack Open Circuit, Front Left Leveling Jack Short to Battery, Front Left Leveling Jack Short to Ground, Front Right Leveling Jack Open Circuit, Front Right Leveling Jack Short to Battery, Front Right Leveling Jack Short to Ground, Leveling Jack, Leveling Jack Extend Valve Open Circuit, Leveling Jack Extend Valve Short to Battery, Leveling Jack Extend Valve Short to Ground, Leveling Jack Retract Valve Open Circuit, Leveling Jack Retract Valve Short to Battery, Leveling Jack Retract Valve Short to Ground, Over Maximum Initial Throttle Position Sensor Voltage, Rear Deck Extend Valve Short to Battery, Rear Deck Extend Valve Short to Ground, Rear Deck Retract Valve Open Circuit, Rear Deck Retract Valve Short to Battery, Rear Deck Retract Valve Short to Ground, Rear Left Leveling Jack Open Circuit, Rear Left Leveling Jack Short to Battery, Rear Left Leveling Jack Short to Ground, Rear Right Leveling Jack Open Circuit, Rear Right Leveling Jack Short to Battery, Rear Right Leveling Jack Short to Ground
Rear Deck Extend Valve Open Circuit · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Fault code 26 on JLG scissor lifts covers a group of open circuit, short to battery, and short to ground faults on the leveling jack valves (front left, front right, rear left, rear right) and related deck extend/retract valve circuits. It is reported by the I/O module during normal operation or system test when the controller sees an electrical condition on one of these valve circuits that does not match expected behavior.
Medium severity. This code does not itself indicate a runaway hydraulic event or immediate safety failure, but a leveling jack or deck valve that will not respond correctly can affect machine setup and stability. Diagnose before relying on the leveling or deck system for a lift.
What does JLG Scissor Lift error code 26 mean?
Fault code 26 is a shared code covering multiple wiring and valve conditions across the leveling jack and deck extend/retract circuits on JLG scissor lifts. The exact fault text displayed depends on which specific condition and which valve or jack location triggered it, for example 'Front left leveling jack short to ground' or 'Leveling jack retract valve short to battery.'
The I/O module monitors the electrical circuits that drive each leveling jack solenoid valve and each deck extend/retract valve. It expects the circuit to behave like a normal solenoid load: current flows within an expected range when energized, and reads open when not. If the module instead sees a circuit that is broken (open circuit), stuck high (short to battery), or stuck low (short to ground), it sets fault code 26 with a description matching the specific valve or jack location involved.
This same code number is also documented for an unrelated condition, 'Over Maximum Initial Throttle Position Sensor Voltage,' which is listed among the code 26 descriptions but is not a leveling jack or deck valve circuit fault. If your analyzer shows this description instead, treat it as a throttle position sensor issue rather than a valve wiring issue.
Common causes of 26
- Damaged, pinched, or chafed wiring to a leveling jack valve (front left, front right, rear left, or rear right) causing a short to ground or short to battery
- Damaged or chafed wiring to a deck extend or retract valve (front or rear) causing a short to ground or short to battery
- A broken wire, disconnected connector, or failed pin causing an open circuit on a leveling jack or deck valve coil
- A failed solenoid coil on a leveling jack extend or retract valve, or on a deck extend or retract valve
- Corrosion or moisture intrusion at a valve connector causing an intermittent short or open condition
- A failed I/O module driver circuit for the affected valve output
How to troubleshoot JLG Scissor Lift 26: first checks
- Note the exact fault description shown on the analyzer or display. Since code 26 covers many different valves and jacks, the specific wording tells you which circuit to inspect first (for example, front left leveling jack versus rear deck extend valve)
- With power removed, visually inspect wiring harnesses running to the affected leveling jack or deck valve for chafing, pinch points, corrosion, or disconnected connectors
- Check the valve connector and pins for corrosion, bent pins, or loose terminals, and clean or reseat as needed
- Measure resistance across the affected solenoid coil to check for an open winding or a short, comparing left/right or front/rear valves against each other if a working reference is available
- Inspect ground connections and battery-side wiring near the affected valve for shorts, especially if the fault reads as short to battery or short to ground
- Check for the throttle position sensor variant of this code if the displayed text mentions throttle position rather than a jack or deck valve, since it requires different diagnostics
How the code clears
No separate clearing step is listed for this code. Once the underlying wiring, connector, or valve fault is repaired, the fault should clear on its own after a normal power cycle or system test, but always confirm the leveling jack and deck valve functions operate correctly before returning the machine to service.
Frequently asked questions
What does JLG fault code 26 mean?
It means the I/O module detected an electrical fault, either an open circuit, a short to battery, or a short to ground, on one of the leveling jack valve circuits (front left, front right, rear left, rear right) or one of the deck extend/retract valve circuits. The exact description shown tells you which specific valve or jack is affected.
Is fault code 26 the same for every JLG scissor lift?
The code number is shared across many related fault descriptions covering leveling jacks and deck valves, plus one unrelated throttle position sensor voltage fault. Always check the exact text displayed on your analyzer to know which condition you are dealing with.
Can I still operate the lift with fault code 26 active?
Since this affects leveling jack and deck valve circuits, operating with an active fault risks incorrect leveling or deck positioning. Diagnose and repair the wiring or valve issue before relying on these functions for setup or operation.
What is the difference between short to battery and short to ground on this code?
Short to battery means the valve circuit is seeing voltage it should not, usually from chafed wiring contacting a powered circuit. Short to ground means the circuit is grounding out unexpectedly, often from chafed wiring touching the frame or a grounded component. Both point to wiring damage but require checking different parts of the circuit.
Why does my analyzer show a leveling jack fault but the machine seems level?
The fault is based on the electrical condition of the valve circuit, not directly on machine level. A wiring or connector fault can trigger code 26 even if the jack has not moved or the deck appears level, because the controller is reacting to the circuit signal it receives, not the physical position.
Does fault code 26 require replacing the solenoid valve?
Not necessarily. Many cases are caused by wiring damage, connector corrosion, or loose pins rather than a failed valve coil. Check wiring and connectors first, and only replace the valve coil if resistance testing confirms an open or shorted winding.
Where do I find which valve or jack is affected?
The analyzer or display shows the specific fault description text, such as 'Rear right leveling jack short to battery' or 'Front deck extend valve open circuit.' This text, not just the code number, tells you exactly which circuit to inspect.