Up Limit Switch Fault Detected
What does SKYJACK-15 mean?
The SKYJACK-15 (Skyjack) EV fault code means: Up Limit Switch Fault Detected. This is a moderate severity code.
Common Symptoms
- Platform LCD on the upper control box displays code 15
- Lift-up function is blocked or stops partway through the raise cycle
- Machine will not raise to full height even though drive and steer still work
- Controller cannot confirm the platform has reached the elevated position
- Drive speed does not derate to creep speed as expected when platform is raised
- Platform lowers normally but raises are intermittent or refused entirely
- Yellow or red fault indicator is lit on the upper control box
Probable Causes (Ranked by Likelihood)
- Up limit switch contacts worn, stuck open, or failed internally Very Likely
- Up limit switch actuator arm bent, broken, or missing so the cam never trips the switch Very Likely
- Wiring harness to the up limit switch chafed, corroded connector, or broken wire causing an open circuit Likely
- Switch mounting bracket loose or shifted so the scissor arm no longer contacts the actuator at the correct travel point Likely
- Water or debris intrusion into the switch housing causing intermittent contact Possible
- GCON or RDC2 controller input channel fault misreading a good switch signal Less Likely
Step-by-Step Diagnostic Procedure
Start at the upper control box. Power the machine on and check whether code 15 is present immediately at rest or only after attempting a lift. An immediate fault at rest suggests a wiring open circuit. A fault that appears only at full height suggests the switch is not being physically actuated.
Locate the up limit switch on the scissor arm or chassis rail. On most SJIII series machines it sits near the top of the inner scissors where a cam or strike plate contacts the actuator at full elevation. Inspect the actuator arm visually for bends, breaks, or missing hardware before touching anything else.
With the machine powered OFF and platform fully lowered, unplug the switch connector. Use a multimeter set to continuity or resistance. With the actuator at rest (not depressed), the switch should read open (no continuity) on a normally-open circuit. Manually press the actuator by hand. You should get continuity. If you get no change either way, the switch has failed internally. Replace it.
Inspect the connector pins and wiring back toward the control module. Look for corrosion, spread pins, or chafed insulation. Wiggle the harness while watching the multimeter. Any flickering reading confirms an intermittent wire break.
Check the switch mounting bracket. The switch must be positioned so the cam or strike plate on the scissor arm fully depresses the actuator at maximum lift height. Loosen the mounting fasteners, reposition the switch closer to the contact point, and re-tighten. Retest a full raise cycle.
If wiring and switch check out good, measure the signal wire voltage at the GCON or RDC2 controller input with the machine powered on. You should see a voltage change (typically 0 V to battery voltage or vice versa) as you manually actuate the switch. No change at the controller input with a confirmed good switch points to a wiring fault between the switch and the controller.
If all field checks pass and the fault remains, connect the Skyjack diagnostic harness via the EZcal / Pcal handheld to read live input states. This will confirm whether the controller is reading the switch input correctly. A mismatch between physical switch state and controller reading indicates a failed controller input channel, which requires advanced diagnosis.
Frequently Asked Questions
What does Skyjack code 15 mean?
Code 15 means the controller is not getting a valid signal from the up limit switch. That switch tells the machine when the platform has reached full elevation. Without that confirmation, the controller may block the lift-up function or refuse to derate drive speed correctly for elevated travel.
Can the machine still run with code 15 active?
Usually yes in a limited way. Drive and lower functions often still work, but lift-up may be blocked or restricted. Do not try to work around it by cycling power repeatedly. The machine may allow partial operation but it is not in a safe, fully-confirmed state until the fault is resolved.
How much does it cost to fix code 15?
If the switch itself failed, a replacement limit switch runs about $20 to $60 in parts. DIY repair with basic tools is straightforward if you are comfortable with electrical connectors. A rental yard or shop will typically charge $150 to $350 total depending on how long diagnosis takes and local labor rates.
Is this dangerous to ignore on a job site?
Yes. The up limit switch is a safety input. On most Skyjack models it also controls drive speed derate at height. If the machine cannot confirm the elevated state, it may drive at full speed while elevated, which raises tip-over risk. Tag the machine out of service until the fault is cleared.