JLG Scissor Lift 66 Fault Code: CAN Bus Failure
Also called Communication Failure, Engine Controller CAN Communication Lost, Indicates Vehicle Communication (CAN Bus) Problems - Accessory CAN Communication Lost, Indicates Vehicle Communication (CAN Bus) Problems - CAN Bus Failure - Power Module, Indicates Vehicle Communication (CAN Bus) Problems - CAN Bus Failure - Load Sensing System Module, Indicates Vehicle Communication (CAN Bus) Problems - CAN Bus Failure - Platform Module, LSS Not Sending CAN Messages, Two Platform Modules Detected
CAN Bus Failure · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Fault code 66 flags a lost CAN bus message between the ground control system and another module: the load sensing system module, the platform module, the power module, an OEM accessory module, or the engine controller. Depending on which link drops, the machine may cut out load-affected functions, block platform operation, or prevent drive, steer, and lift. Priority is listed as 10.
High severity. This code can disable drive, steer, and lift functions or block all platform controls depending on which module lost communication, so it should be treated as a stop-and-diagnose condition rather than something to run through a shift.
What does JLG Scissor Lift error code 66 mean?
Fault code 66 is a general CAN bus communication failure code on JLG scissor lifts. The CAN bus is the digital network that lets the ground control module talk to other modules on the machine: the load sensing system, the platform control box, the power module, OEM accessory modules, and in some configurations the engine controller. When one of these modules stops sending its expected message in time, the control system logs code 66 and reacts by disabling the functions tied to that module.
There are several distinct triggers behind this one code, and the actual effect on the machine depends on which module went silent. If the load sensing system module stops reporting, the machine may treat itself as overloaded. If the platform module goes quiet, platform controls are locked out but ground mode still works. If the power module stops communicating, drive, steer, and lift up are prevented. If an OEM accessory module drops out, motion interlocks are removed. If the engine controller is CAN controlled and stops communicating, the fault is reported for that link as well.
In every case the fault is retained until power is recycled, meaning simply clearing the immediate symptom will not clear the fault code from memory.
What triggers a JLG Scissor Lift 66 code?
The control system sets this fault under several specific conditions. If the load cell message (0x80) from the load sensing system module is not received for 1000 milliseconds while machine setup has load set to CUTOUT PLT or CUTOUT ALL, the fault sets and the vehicle is assumed overloaded. If the digital input motion message (0x00) from the platform module is not received for 1000 milliseconds while platform mode is selected, the fault sets and all platform functions are prevented. If an accessory control 1 message is received once from an OEM accessory module but a follow-up message is not received within 1000 milliseconds, the fault sets and no motion interlocks remain active. If the power module status message (0x24) is not received for 1000 milliseconds, or the power module itself reports a CAN bus difficulty fault code (0x09), the fault sets and drive, steer, and lift up are prevented. All of these conditions are retained until power is recycled.
Common causes of 66
- Load sensing system module (LSS) is not sending its load cell CAN message, so the control system stops receiving it while load cutout settings are active.
- Platform module is not sending its digital input motion message while the machine is in platform mode, cutting off platform control communication.
- An OEM accessory module fails to maintain ongoing CAN bus communication with the ground module after an initial message is received.
- Power module stops sending its status message, or the power module itself has logged an internal CAN bus difficulty fault.
- Wiring damage, corrosion, or loose connections at the load sensing system module, along the scissor arms leading up to the platform, at the platform and ground control boxes, or at the power module and ground control box.
- Engine controller configured for CAN control is not communicating with the rest of the vehicle network.
- Two platform modules detected on the network at the same time, which can confuse message routing and produce the same communication loss symptoms.
How to troubleshoot JLG Scissor Lift 66: first checks
- Note which functions are affected: overload-style cutout points to the load sensing system module, loss of platform control points to the platform module, loss of drive/steer/lift points to the power module.
- Inspect wiring and connectors at the load sensing system module and along the scissor arms leading up to the platform for chafing, pinching, or corrosion.
- Inspect wiring at the platform and ground control boxes, again following the harness runs up the scissor arms.
- Inspect wiring at the ground control box and at the power module for loose or damaged connectors.
- If an OEM accessory is installed, check that accessory's own documentation for wiring and CAN communication troubleshooting steps specific to that unit.
- Confirm no other CAN bus difficulty fault (0x09) is present on the power module, since that alone can trigger this code.
- Verify only one platform module is present on the network if two-module detection is suspected.
How the code clears
This fault is retained in the control system until power is recycled. Recycling power alone may not fix the underlying wiring or module issue, but it is required to clear the fault from memory after the communication problem has been corrected. For the power module related cause specifically, recycling power to clear the difficulty is listed directly as part of the resolve. No other separate clearing step is listed beyond correcting the wiring or module issue and cycling power.
Frequently asked questions
What does JLG fault code 66 mean?
It means the control system lost expected CAN bus communication from another module on the machine, which could be the load sensing system module, the platform module, the power module, an OEM accessory module, or the engine controller if it is CAN controlled.
Why did my scissor lift suddenly act like it's overloaded?
If the load sensing system module stops sending its load cell message for 1000 milliseconds while load cutout settings are active, the control system assumes the vehicle is overloaded and cuts out load-affected functions, even if the machine is not actually overloaded.
Why won't the platform controls respond but ground mode still works?
This happens when the platform module stops sending its motion message for 1000 milliseconds while platform mode is selected. All platform functions are blocked, but the machine falls back to normal operation from ground mode.
Why are drive, steer, and lift up all disabled at once?
That combination points to the power module. If its status message is not received for 1000 milliseconds, or if the power module has logged its own CAN bus difficulty fault, drive, steer, and lift up are all prevented.
Will cycling the key clear fault code 66?
Recycling power is required to clear the fault from memory since it is retained until power is recycled, but the underlying wiring or module problem needs to be found and fixed first or the fault will likely return.
Does an OEM accessory installed on the machine cause this fault?
Yes, if an OEM accessory module sends an initial message but then fails to maintain communication within 1000 milliseconds, code 66 sets and motion interlocks are removed. Check that accessory's own documentation for troubleshooting.
Can two platform modules on one machine cause this code?
Yes, having two platform modules detected on the network is listed as a related condition and can interfere with normal CAN messaging, producing the same communication loss symptoms as a single failed module.