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JLG 600AJ Intermittent Platform Communication Loss

JLG·600AJ·Deutz D2.9 L4 / GM 3.0L·Advanced·3-4 hours·0 views

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The boom lift occasionally loses all platform control communication mid-operation, shutting down all movement. Once the boom is moved to a different angle, communication may restore. This is a common indicator of a broken or worn conductor inside the boom cable cat-track or harness transition joints.

Symptoms

Platform displays drop out, showing 'PCON Link Error' or blank screens
Operations run for short intervals, then completely park with platform alarms ringing
Status errors indicate active CAN network fault 9-9 or 4-1
Boom actions function with Ground controls but fail intermittently when using Platform controls

Possible Causes

Broken, stretched, or internally severed structural wiring within the main telescope cat-track
Loose pin contacts in the primary mid-boom strain Relief/Bulkhead connection plug
Water intrusion causing signal grounding inside the platform junction box module
Damaged, shorted, or ungrounded CAN-Bus shielding connection lines

Diagnostic Procedure

1
Perform Physical Inspection of the Telescope Cable Track
Visually inspect the flexible plastic cable cat-track along the boom. Check for crushed, crimped, or twisted areas of the harness wrapper that signal core conductor stretch or severe pinches.
2
Conduct CAN-Bus Resistance and Signal Static Checks
Switch off keyswitch and battery disconnect. Measure cross-resistance of CAN-High to CAN-Low pins at the platform control box connector plug (expected target is 60 Ohms). If reading 120 Ohms, one termination resistor is missing/disconnected; if infinity, CAN loop is severed.
3
Perform dynamic Flex Wiring Continuity Verification
Attach your digital multimeter with a min/max recorder to the critical CAN+ or power lines at both GCM and Platform box ends. Manually articulate the telescope/jib boom segments. Monitor for instantaneous spikes in resistance or total continuity dropouts.
4
Check Platform Power Supply Feeds under Load
Verify voltage across Pin A (12V Supply) and Pin B (Ground) at the Platform Control Module plug while running functions. Voltage must remain stable above 12.0V DC. If voltage dips severely during joystick movements, look for broken power leads in the boom track.

Common Repairs

Replacing the platform master harness loom routed inside the CAT-track
Splicing and heat-shrinking damaged electrical conductors in the junction box
Replacing or cleaning corroded Deutsch connector plugs and pins at the boom joints

Safety Precautions

Perform diagnostics from the Ground Control Panel when boom adjustments are required during testing
Never perform repairs inside the cable track while the boom is actively extended or high in the air

Required Tools

Digital Multimeter (DMM) with Min/Max hold
JLG Machine Analyzer Tool
Deutsch Crimping Tool Set / Pins
Heat Shrink Tubing and Heat Gun

Related Fault Codes

9-9 (CAN bus master failure)4-1 (Platform-to-ground communication fault)

Related Repair Cases

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