Caterpillar Excavator Fault Code 444-6: Complete Diagnostic & Repair Guide

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What is Caterpillar Fault Code 444-6?

Caterpillar Fault Code 444-6 indicates a "Transmission/Implement Pump Solenoid #2 — Current Below Normal," signaling that the ECM has detected an abnormally low current condition in the solenoid control circuit.

This code targets the hydraulic implement pump control circuit, specifically the solenoid responsible for regulating hydraulic flow to work tool functions. The ECM continuously monitors current draw through this solenoid driver circuit. When current falls below the expected threshold, it triggers a 444-6 active fault.

On used Caterpillar excavators, this fault is particularly critical because it directly impacts hydraulic implement performance, potentially causing reduced productivity or complete loss of tool function.

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Common Symptoms

• Active warning lamp or MID/CID alert displayed on the monitor panel
• Loss of implement hydraulic function — bucket, boom, or stick response may be sluggish or non-responsive
• Engine or hydraulic derate mode activated to protect the system
• Intermittent solenoid chatter or erratic implement movement during operation
• Diagnostic codes stored in the ECM history alongside related hydraulic fault codes

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Potential Causes

• Open circuit in the solenoid wiring harness due to chafing, breakage, or a pulled connector pin
• Failed or shorted solenoid coil with resistance outside the specified range (typically 7–25 ohms for Cat solenoids)
• Corroded or moisture-contaminated connectors — extremely common on used machines with field exposure
• Damaged ECM output driver — rare, but possible after voltage spike events
• Harness friction points near boom pivot areas, a known wear location on older Cat excavators

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How to Troubleshoot and Fix Code 444-6

Step 1 — Preliminary Inspection Begin with a thorough visual inspection of the solenoid harness from the ECM connector to the solenoid body. On used excavators, pay close attention to harness routing near boom pivot points and hydraulic hose bundles — these are high-wear friction zones. Look for cracked insulation, corrosion, or pulled pins.

Step 2 — Connector & Continuity Check Disconnect the solenoid connector and use a digital multimeter to measure solenoid coil resistance. A healthy Cat implement solenoid typically reads between 7–25 ohms. A reading of OL (open loop) confirms a failed coil. Next, perform a continuity test along the entire harness back to the ECM connector pin to identify any open circuits.

Step 3 — Voltage & ECM Output Verification Using Cat ET (Electronic Technician) diagnostic software, command the solenoid ON via the override function. Monitor voltage output at the solenoid connector — you should see battery voltage (approximately 24V DC) when commanded active. No voltage indicates a wiring or ECM driver fault.

Step 4 — Component Replacement Replace the solenoid if resistance is out of spec. Repair or replace damaged harness sections using proper weatherproof connectors. Clear codes with Cat ET and retest under load.

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Disclaimer: This guide is intended for reference purposes only. Always consult a certified Caterpillar dealer or licensed heavy equipment technician before performing repairs. Improper diagnosis or repair may void warranties and create safety hazards.