What is Caterpillar Fault Code 2423-6?

Caterpillar Fault Code 2423-6 indicates a Current Below Normal or Open Circuit condition on the Hydraulic Fan Speed Solenoid control circuit.

This code is generated when the Engine Control Module (ECM) detects that the current flowing through the hydraulic fan solenoid circuit has dropped below the expected threshold — or has been lost entirely. The hydraulic cooling fan system is critical for maintaining proper engine and hydraulic oil temperatures, making this fault a high-priority issue on any Caterpillar excavator.

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Common Symptoms

When fault code 2423-6 is active, operators typically experience:

• Active fault warning displayed on the monitor panel or Cat ET diagnostic tool
• Cooling fan running at maximum speed continuously (fail-safe mode), causing excessive fuel consumption and noise
• Engine or hydraulic system overheating if the fan defaults to a low-speed or inoperative state
• Reduced machine performance or automatic power derate in some configurations
• Erratic fan behavior, such as sudden speed changes during operation

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Potential Causes

The following are the most common technical causes of this fault, particularly on used or high-hour machines:

• Failed or open-circuit hydraulic fan solenoid — internal coil burnout is common on older units
• Damaged wiring harness — chafing, pinching, or heat damage near the engine compartment or hydraulic pump area
• Corroded or loose connector pins at the solenoid or ECM harness connector
• Broken signal wire between the ECM and the fan solenoid
• Faulty ECM output driver — less common, but possible after electrical surges or moisture intrusion

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How to Troubleshoot and Fix Code 2423-6

Step 1 — Connect Cat ET Diagnostic Software Connect a laptop running Caterpillar ET (Electronic Technician) to the machine's diagnostic port. Confirm the active fault, log any related codes, and monitor real-time fan solenoid command data.

Step 2 — Inspect the Harness and Connectors Physically trace the wiring harness from the ECM to the hydraulic fan solenoid. On used excavators, pay close attention to known rub points near frame edges, hydraulic lines, and heat shields. Look for cracked insulation, bare wires, or corrosion on connector pins. Clean corroded pins with electrical contact cleaner before drawing conclusions.

Step 3 — Test Solenoid Resistance Disconnect the solenoid connector and use a digital multimeter to measure resistance across the solenoid terminals. A healthy solenoid typically reads between 8–12 ohms (verify against your specific model's service manual). An open reading (OL) confirms solenoid failure.

Step 4 — Check Circuit Continuity and Voltage With the harness reconnected and ignition on, verify the supply voltage at the solenoid connector matches ECM command specs. Test wire continuity back to the ECM connector to rule out broken circuits.

Step 5 — Replace and Retest Replace any failed components — solenoid, damaged harness sections, or connector pins. Clear the fault using Cat ET and perform a functional test to confirm normal fan operation.

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Disclaimer: This guide is intended for informational purposes and general diagnostic direction. Always refer to the official Caterpillar Service Manual for your specific machine configuration. Complex electrical or ECM-related repairs should be performed by a certified Cat dealer technician or qualified heavy equipment mechanic.