JLG Articulating Boom Lift 66 Fault Code: Problems with the CAN Bus
Also called BLAM CAN Communications Lost, CAN Bus, Chassis CAN Communications Lost, Cylinder Load Pin CAN Communications Lost, Engine Controller CAN Communications Lost, Excessive CAN Bus Communication Errors, Main Angle Sensor 1 (Right) CAN Bus Communications Lost, Main Angle Sensor 2 CAN Communications Lost, Platform CAN Communications Lost
Problems with the CAN Bus · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Fault code 66 is a priority 10 fault covering several related CAN bus communication losses between JLG modules (platform, ground, chassis, BLAM, cylinder load pin, power module, main boom angle sensors, or UMS module). It almost always points to wiring problems between two modules on the CAN bus, or in one variant, excessive bus errors (more than 500 bus off or bus passive conditions in the current power cycle).
High severity. This is listed as a priority 10 fault. CAN bus loss can disable communication between the platform and ground controls, which affects safe operation of the machine. Treat it as a stop-and-diagnose issue before continuing to operate.
What does JLG Articulating Boom Lift error code 66 mean?
Fault code 66 covers a family of CAN bus communication faults reported between the various control modules on a JLG articulating boom lift: the platform module, ground module, chassis module, power module, BLAM (Boom Length Angle Module), cylinder load pin, UMS sensor module, and on 1250AJP machines, the main boom angle sensors #1 and #2.
In every variant, the core problem is the same: one control module has stopped receiving CAN messages from another module it depends on. The description text repeatedly points to wiring problems between the two modules involved as the probable cause, though one variant is specifically an excessive-error condition on the bus itself rather than a single broken link.
Because the BLAM sits in the trunk of the CAN bus, losing communication with it can cascade: if power is lost to the BLAM, the cylinder load pin also loses power, which will trigger the Cylinder Load Pin CAN Communications Lost fault alongside it. If you see multiple CAN-related faults active together, start by checking whether the BLAM's connections and power are intact.
What triggers a JLG Articulating Boom Lift 66 code?
The excessive CAN bus communication errors variant sets when the ground module detects more than 500 bus off conditions or more than 500 bus passive conditions during the current power cycle. The other variants under code 66 are described as a specific module not receiving CAN messages or acknowledgments from another module, without a separate numeric threshold given for those cases.
Common causes of 66
- Wiring problems between the platform and ground modules (most common cause listed for platform CAN communications lost and related CAN bus failure variants)
- Wiring problems between the BLAM and ground modules, or between the platform and chassis modules where the BLAM connection is involved
- Wiring problems between the chassis and ground modules on machines equipped with a chassis module
- Wiring problems between the cylinder load pin and ground module on machines equipped with a cylinder load pin
- Wiring problems between the ground and power modules, or at the platform/ground module connections tied to the 48-volt protection circuit tripping
- Faulty bus wiring, faulty termination resistors, unwanted capacitance on the bus, or a module that has stopped communicating, all listed as causes of excessive bus off/bus passive error counts
- Loss of CAN communications with main boom angle sensor #1 or #2 on 1250AJP machines
How to troubleshoot JLG Articulating Boom Lift 66: first checks
- Check for other active CAN-related faults at the same time. Because the BLAM carries the CAN bus trunk, multiple faults appearing together (for example along with a Cylinder Load Pin CAN Communications Lost fault) points toward a BLAM wiring or power issue rather than several separate failures
- Inspect connectors and wiring harnesses between the platform and ground modules first, since this is the most frequently cited wiring path in the fault descriptions
- If the machine has a chassis module, cylinder load pin, or BLAM, inspect the wiring runs specific to those modules as listed in the applicable fault variant
- Look for loose, corroded, or damaged connector pins at each module connection point along the CAN bus, and check that connectors are fully seated
- Check CAN bus termination resistors and wiring for damage if the excessive bus error variant is present, since faulty termination or wiring capacitance is called out as a cause
- Verify the 48-volt protection circuit and related wiring at the platform and ground modules if a power module CAN bus failure or 48V protection tripped condition is indicated
- On 1250AJP machines showing loss of communication with a main boom angle sensor, check the wiring and connections specific to that sensor
How the code clears
No separate clearing step is listed for this code. Standard practice is to repair the wiring or connector problem identified, then cycle power to the machine and confirm the fault does not return before resuming operation.
Frequently asked questions
What does JLG fault code 66 mean?
It means one or more control modules on the machine's CAN bus have lost communication with another module, or the ground module has detected an excessive number of bus errors. The exact wording on your display (platform, chassis, BLAM, cylinder load pin, power module, or angle sensor communications lost) tells you which specific link is affected.
Is fault code 66 safe to keep operating with?
No. This is a priority 10 fault, and CAN communication loss can affect the machine's ability to safely relay control and sensor data between the platform and ground. Stop operation and diagnose the wiring issue before continuing to use the lift.
Why do multiple CAN faults show up at the same time?
Because the BLAM carries the trunk of the CAN bus, a lost connection there can cut power to other modules downstream, such as the cylinder load pin. Seeing several CAN-related faults together is a clue to check the BLAM's wiring and power supply first.
What usually causes fault code 66?
Wiring problems between the two modules named in the specific fault description are the most commonly listed cause. Faulty bus wiring, bad termination resistors, or excess capacitance on the bus are also listed as causes when the fault is tied to excessive bus off or bus passive error counts.
What is the difference between bus off and bus passive errors?
Both are counted toward the excessive CAN bus communication errors variant of this fault, which sets once the ground module logs more than 500 bus off conditions or more than 500 bus passive conditions in the current power cycle. Both point to unreliable communication on the CAN bus rather than a single broken wire.
Does fault code 66 apply to all JLG boom lift models?
The general platform, ground, and chassis module variants apply broadly. Some variants are model-specific, such as the main boom angle sensor #1 and #2 communications lost faults, which are noted as occurring only on the 1250AJP.
Is there a reset procedure for fault code 66?
No reset procedure is listed for this code. Repair the underlying wiring or module connection issue first, then cycle power and confirm the fault clears before returning the machine to service.