JLG Boom Lift 66 Fault Code: Problems with the CAN Bus
Problems with the CAN Bus · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Fault code 66 on JLG M600 boom lifts points to a problem with the CAN Bus network that links the power module, platform module, and ground module. Depending on the exact condition, it can mean the 48V protection circuit has tripped or that one of the three modules is not communicating with the others. It almost always traces back to wiring problems between modules.
High severity. This code affects the communication backbone between the machine's control modules. Until it's resolved, the platform controls, ground controls, and power module may not reliably talk to each other, which can affect machine function and operator control. Treat it as a stop-and-diagnose issue before continued operation.
What does JLG Boom Lift error code 66 mean?
Fault code 66 covers a family of CAN Bus communication problems on the JLG M600 boom lift. The CAN Bus is the wiring network that lets the power module, platform module, and ground module send and receive data from each other, things like operator inputs, sensor readings, and system status. When one module stops hearing from another, the system can't trust that commands and safety interlocks are being passed along correctly.
There are four distinct conditions described under this code. One involves the 48V protection circuit tripping because the power module isn't getting acknowledgments back from either the platform or ground module. The other three are more direct CAN bus failures, each named for which module has gone silent: the ground module, the platform module, or the power module itself.
In every case, the root issue described is wiring, whether it's a break, corrosion, loose connector, or damaged cable somewhere in the run between modules.
Common causes of 66
- 48V protection tripped: wiring problems at the platform or ground module preventing the power module from receiving acknowledgments to transmitted data
- CAN bus failure, ground module: the power module hears the platform module but not the ground module, described as a condition that should not be possible under normal operation
- CAN bus failure, platform module: wiring problems between the platform and ground modules, where the power module hears the ground module but not the platform module
- CAN bus failure, power module: wiring problems between the ground and power modules, where the power module gets no acknowledgments from either the platform or ground module
How to troubleshoot JLG Boom Lift 66: first checks
- Inspect all CAN bus wiring and connectors between the power module, platform module, and ground module for corrosion, looseness, chafing, or physical damage
- Check connector pins at each module for bent, backed-out, or corroded terminals, since a poor pin connection can interrupt communication without an obvious break in the cable
- Trace the wiring runs specifically between the platform and ground modules and between the ground and power modules, since the described causes point to breaks in these specific sections
- Verify grounds and power supply to each module are solid, since an intermittent power module supply can look like a communication fault
- Look for pinch points, rub-through, or moisture intrusion along the boom and turntable where CAN wiring flexes repeatedly during operation
How the code clears
No reset procedure is listed for this code. Once the wiring problem causing the communication loss is found and repaired, the fault should clear on its own as the modules resume normal acknowledgments. If it doesn't clear after a wiring repair, recheck connector seating at all three modules before assuming a module itself has failed.
Affected models and serial ranges
66 appears in our records across 1 JLG Boom Lift models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| M600 | Serial range not listed in source records |
Frequently asked questions
What does JLG fault code 66 mean on an M600 boom lift?
It means the CAN Bus network connecting the power module, platform module, and ground module has a communication problem. This could be a tripped 48V protection circuit or one module not receiving acknowledgments from another, and it's almost always caused by wiring issues between modules.
Can I keep operating the lift with fault code 66 active?
It's not recommended. This fault affects the communication network that carries commands and status information between control modules. Continuing to operate with unreliable communication between modules is a safety risk, so the machine should be diagnosed and repaired before further use.
Which wiring should I check first for code 66?
Start with the CAN bus wiring and connectors between whichever modules the specific fault description names. If it's a platform module failure, check wiring between the platform and ground modules. If it's a power module failure, check wiring between the ground and power module.
Why does the description say a certain failure 'should not be possible'?
That note applies to the case where the power module hears the ground module but not the platform module. Given how the network is wired, this pattern isn't expected under normal fault conditions, so if you see it, treat it as a sign of a more unusual wiring or module problem rather than a simple broken connection.
Does fault code 66 point to a bad module or just bad wiring?
The available information points to wiring problems as the probable cause in every listed condition. There is no mention of a module needing replacement, so wiring and connectors should be fully ruled out before considering a module swap.
Will the fault clear itself after I fix the wiring?
There is no separate clearing step listed. In most cases, repairing the faulty wiring restores communication and the fault should clear on its own once the modules resume normal acknowledgments.