What is Caterpillar Fault Code 1347-6?

Fault Code 1347-6 indicates a "Fuel Injector Solenoid Circuit - Current Below Normal" condition on Caterpillar excavators and heavy equipment. This diagnostic trouble code (DTC) means the Electronic Control Module (ECM) has detected abnormally low electrical current flowing through one or more fuel injector solenoid circuits during engine operation.

The fuel injector solenoids are critical components that control precise fuel delivery into the combustion chambers. When the ECM sends electrical signals to these solenoids, they open and close to meter fuel at exact intervals. The 1347-6 code specifically identifies that the current draw is below the manufacturer's specified threshold, typically indicating an open circuit, high resistance, or failing solenoid. This fault directly impacts engine performance, fuel efficiency, and emissions compliance—making it essential to address promptly on used excavators where wiring and connector degradation are common.

Common Symptoms

When Fault Code 1347-6 is active, operators may experience:

• Check Engine Light or Malfunction Indicator Lamp (MIL) illuminated on the instrument cluster
• Noticeable rough idle or engine misfiring, particularly under load
• Loss of power or reduced engine performance during digging or lifting operations
• Increased black or white smoke from the exhaust due to incomplete combustion
• Hard starting conditions, especially during cold weather operation

Potential Causes

The most common technical reasons for Code 1347-6 on used Caterpillar excavators include:

• Damaged or corroded wiring harness connections at the fuel injector solenoid connector (common wear point in high-vibration environments)
• Failed fuel injector solenoid with internal open circuit or degraded coil windings
• Chafed or broken wires along harness routing points where contact with engine components occurs over time
• Corroded pins or moisture intrusion in the injector harness connectors (especially prevalent in used machines)
• Faulty ECM injector driver circuit (less common but possible in high-hour machines)
• Poor ground connections at the engine block or chassis grounding points

How to Troubleshoot and Fix Code 1347-6

Step 1: Connect Diagnostic Software Use Caterpillar Electronic Technician (Cat ET) or compatible diagnostic software to identify which specific cylinder's injector circuit is triggering the fault. Record all active and logged codes, and note the failure mode identifier (FMI) details.

Step 2: Visual Harness Inspection Perform a thorough visual inspection of the injector wiring harness from the ECM to each fuel injector. On used excavators, pay special attention to harness routing near hot exhaust components, sharp edges, and mounting brackets where abrasion commonly occurs. Check all connector pins for corrosion, bent contacts, or moisture intrusion—clean or replace connectors as needed.

Step 3: Electrical Testing Disconnect the suspected fuel injector solenoid connector and measure resistance across the solenoid terminals using a quality digital multimeter. Typical resistance values range from 0.3 to 2.0 ohms (consult your specific service manual). Readings significantly higher or showing infinite resistance indicate a failed solenoid requiring replacement.

Step 4: Circuit Continuity and Voltage Checks With the harness connector disconnected at the injector, check for continuity between the ECM connector and the injector harness connector to identify any open circuits. Also verify battery voltage is present at the power supply wire when the key is on. Test the ground circuit integrity by measuring resistance to chassis ground (should be less than 1 ohm).

Step 5: Component Replacement If testing confirms a failed fuel injector solenoid, replace the affected unit with genuine Caterpillar or OEM-equivalent parts. On used excavators with high operating hours, consider replacing all injector O-rings and seals during this service to prevent future leaks. Clear codes using diagnostic software and perform a test run under load.

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Disclaimer: This guide provides general troubleshooting information for Caterpillar Fault Code 1347-6. Always consult your machine's specific service manual and consider professional diagnostic assistance from a certified Caterpillar technician, especially when working with fuel system components on used equipment with unknown service history.