What is Komatsu PC220-10 Fault Code E-35?

Fault Code E-35 on the Komatsu PC220-10 excavator indicates a malfunction in the engine controller communication circuit, specifically a loss of signal or abnormal communication between the engine ECM (Engine Control Module) and the machine's main monitor system. This code triggers when the engine controller fails to transmit or receive proper diagnostic data through the CAN (Controller Area Network) communication line.

This fault is critical for the PC220-10 because modern Komatsu excavators rely on continuous ECM-to-monitor communication to manage engine performance, fuel efficiency, emission controls, and hydraulic system coordination. When communication breaks down, the machine cannot optimize performance parameters or properly warn operators of developing issues, potentially leading to unexpected shutdowns or reduced operational safety.

Common Symptoms

When Code E-35 is active, operators typically experience:

• Warning lamp illumination on the main monitor display with "E-35" error message showing
• Intermittent or complete loss of engine parameter readings (RPM, coolant temperature, fuel level) on the display
• Engine derating or power reduction mode activation as a protective measure
• Inability to access diagnostic information through the standard monitor interface
• Erratic gauge behavior with engine data flickering or freezing on screen

Potential Causes

The most common technical causes for E-35 in used PC220-10 excavators include:

• CAN bus wiring harness damage from abrasion against frame components, particularly near the engine mount points where vibration causes wire chafing
• Corroded or loose connector pins at the ECM harness plug (common in machines with 3,000+ operating hours)
• Failed termination resistor in the CAN communication circuit causing signal reflection
• ECM internal communication circuit failure due to voltage spikes or water intrusion
• Main monitor control unit malfunction preventing proper signal reception
• Ground connection deterioration at engine block grounding points (typical in high-humidity environments)

How to Troubleshoot and Fix Code E-35

Step 1: Visual Inspection of Communication Harness Perform a thorough inspection of the wiring harness running between the engine ECM (located on the right side of the engine) and the cab monitor. On used excavators, check for wire insulation damage at known rub points: near the swing bearing pass-through, along the engine mounting brackets, and where harnesses contact hydraulic lines. Look for green corrosion on connector terminals and ensure locking tabs are fully engaged.

Step 2: Test CAN Bus Circuit Integrity Using a digital multimeter, disconnect both ends of the CAN communication line and measure resistance between the CAN-H and CAN-L wires. You should read approximately 60 ohms (indicating proper termination resistance at both ends). If reading shows open circuit or infinite resistance, suspect broken wires or failed termination resistors. Check for short circuits to ground by measuring each wire to chassis ground (should read infinite resistance).

Step 3: Verify ECM Power and Ground With ignition on, verify the ECM receives proper voltage (typically 24V) at its power supply pins using your multimeter. Check ground circuit continuity by measuring resistance from ECM ground pins to a known good chassis ground—reading should be less than 0.5 ohms. Clean and tighten all ground connections at the engine block, as corrosion buildup is extremely common in older machines.

Step 4: Utilize Komatsu Diagnostic Software Connect Komatsu KOMTRAX or compatible diagnostic software to the machine's diagnostic port. Monitor live CAN bus traffic to identify whether the ECM is transmitting data or if the monitor is failing to receive. This requires a laptop with appropriate interface cable (typically available through Komatsu dealers). The software can pinpoint whether the fault originates from the sending (ECM) or receiving (monitor) side of the circuit.

Step 5: Component Replacement Priority For used excavators, always replace connectors and repair harness damage before condemning electronic modules. If wiring tests pass, swap the main monitor control unit first (less expensive than ECM replacement). Only replace the engine ECM after confirming all wiring, grounds, and the monitor unit are functioning correctly, as ECM failures are relatively rare compared to harness issues.

---

Disclaimer: This guide provides general troubleshooting information for experienced diesel mechanics. Always consult the official Komatsu service manual for your specific machine serial number, and consider professional diagnostic assistance for complex electrical issues. Improper troubleshooting can damage sensitive electronic components.