What is Kobelco SK350-6E Fault Code 1-1?

Kobelco SK350-6E Fault Code 1-1 indicates an Engine Control Module (ECM) power supply abnormality or voltage irregularity. This diagnostic trouble code (DTC) is triggered when the electronic control system detects insufficient voltage, excessive voltage, or an intermittent power feed to the engine's main computer. On this particular model, which uses Hino J05E or Isuzu engine platforms depending on build year, the ECM requires stable 24-volt DC power to manage fuel injection timing, sensor inputs, and emissions control.

This code is critical because unstable ECM voltage can cause erratic engine behavior, incomplete combustion cycles, and potential damage to sensitive electronic components. In used excavators, deteriorated wiring harnesses and corroded ground connections are the primary culprits behind this fault.

Common Symptoms

• Check engine light illuminated on the instrument cluster with possible engine derate mode activated
• Intermittent loss of engine power or unexpected shutdown during operation
• Difficulty starting the machine, especially after sitting overnight or in cold conditions
• Erratic idle behavior with RPM fluctuations between 800-1200 RPM
• Multiple secondary fault codes appearing simultaneously due to ECM malfunction

Potential Causes

The most frequent technical causes for Code 1-1 on used SK350-6E excavators include:

• Main power harness degradation near the ECM connector (common rub point behind the cab near hydraulic lines)
• Corroded or loose battery terminals and ground connections causing voltage drops
• Failing alternator producing inconsistent charging voltage (should maintain 26-28V during operation)
• Damaged main power relay or corroded relay socket in the electrical junction box
• Internal ECM capacitor failure (more common in machines exceeding 8,000 operating hours)
• Aftermarket electrical accessories drawing excessive parasitic load from ECM circuit

How to Troubleshoot and Fix Code 1-1

Step 1: Verify Battery and Charging System Using a multimeter, check battery voltage at rest (should read 24-26V) and under load during cranking (shouldn't drop below 22V). Test alternator output during operation—voltage should stabilize at 26-28V at 1500 RPM. Replace batteries if they show signs of sulfation or test below 12V per battery.

Step 2: Inspect ECM Power Supply Harness Locate the ECM (typically mounted under the operator's cab floor panel). Disconnect the main harness connector and inspect for:

• Green corrosion on pins (especially power and ground terminals)
• Pushed-back pins causing intermittent contact
• Harness chafing where wiring contacts metal edges near hydraulic pump assembly

Step 3: Test Power Relay and Ground Circuits Check the main power relay in the electrical panel using Kobelco diagnostic software or by swapping with an identical relay. Measure resistance between ECM ground terminal and chassis ground—should read below 0.5 ohms. Clean all ground connection points with wire brush and dielectric grease.

Step 4: Monitor Voltage Under Load With engine running, use diagnostic software (Kobelco genuine or compatible J1939 scanner) to monitor real-time ECM voltage. Voltage drops below 20V or spikes above 30V confirm power supply issues requiring immediate harness replacement.

For used excavators, always inspect wiring for heat damage, rodent chewing, and previous repair attempts using improper connectors before replacing the ECM itself—power supply issues account for 80% of Code 1-1 occurrences.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the official Kobelco service manual for your specific serial number and consider professional diagnostic services for complex electrical issues or warranty-covered repairs.