What is Caterpillar Fault Code 1119-6?

Caterpillar Fault Code 1119-6 indicates a "Fuel Actuator Inlet Metering Valve - Current Below Normal or Shorted to Low Source." This diagnostic trouble code (DTC) signals that the Electronic Control Module (ECM) has detected abnormally low electrical current flowing through the fuel inlet metering valve (IMV) circuit, or the circuit is shorted to ground.

The inlet metering valve is a critical component in Caterpillar's common rail fuel system, controlling the amount of fuel entering the high-pressure fuel pump. When the ECM detects insufficient current flow (typically below the expected 300-800 mA range during operation), it logs this fault code to prevent potential engine damage or performance issues. This code is particularly significant because improper fuel metering directly affects combustion efficiency, power output, and emissions compliance on diesel excavators.

Common Symptoms

When fault code 1119-6 is active, operators may experience:

• Engine derate or reduced power output, limiting excavator performance and hydraulic response
• Hard starting or extended cranking before the engine fires, especially during cold starts
• Rough idle or engine surging due to inconsistent fuel delivery to the injection system
• Amber or red warning lights illuminated on the instrument cluster, possibly with active alarm codes
• Black smoke from exhaust during acceleration, indicating incomplete combustion from improper fuel metering

Potential Causes

The most common technical reasons for code 1119-6 on used Caterpillar excavators include:

• Damaged or corroded wiring harness at connector pins, especially where harnesses route near hot exhaust components or moving parts
• Failed inlet metering valve solenoid with internal short circuit or open coil winding
• Worn or corroded electrical connectors at the IMV or ECM, common on machines with high operating hours
• Chafed wiring at known rub points along the fuel system harness routing, particularly near engine mounts
• ECM internal fault (less common) where the driver circuit has failed
• Poor ground connections causing voltage drop in the low-side circuit

How to Troubleshoot and Fix Code 1119-6

Step 1: Visual Inspection Begin by thoroughly inspecting the inlet metering valve harness from the ECM to the valve itself. Look for obvious damage, corrosion, or wear at connector pins. On used excavators, pay special attention to harness routing near the fuel pump where vibration and heat cause accelerated wear. Disconnect the IMV connector and inspect for moisture, corrosion, or bent pins.

Step 2: Electrical Testing Using a digital multimeter (DMM), measure the resistance of the inlet metering valve solenoid. With the connector disconnected and ignition off, typical resistance should read between 2-8 ohms (consult your specific service manual). A reading of infinite resistance indicates an open circuit, while near-zero resistance suggests a short to ground. Also test harness continuity from the ECM connector to the valve connector.

Step 3: Advanced Diagnostics Connect Caterpillar Electronic Technician (Cat ET) diagnostic software to monitor live current flow to the IMV during cranking and operation. Compare actual current values against specifications (typically 300-800 mA). Check for voltage supply at the valve connector with ignition on—should read battery voltage on the supply wire. If voltage and harness are good but resistance is out of spec, replace the inlet metering valve.

Step 4: Check Ground Circuits Verify the ECM ground connections and engine block grounds are clean, tight, and corrosion-free. Poor grounds are frequently overlooked on used machines and cause numerous current-related fault codes.

Disclaimer: This guide provides general troubleshooting information. Always consult the manufacturer's service manual for your specific machine model and serial number. If you're unfamiliar with high-pressure fuel systems or electrical diagnostics, consult a certified Caterpillar technician to prevent injury or further damage.