Komatsu PC750-7 Fault Code E116: Complete Diagnostic Guide

What is Komatsu PC750-7 Fault Code E116?

Fault Code E116 on the Komatsu PC750-7 indicates a malfunction in the Engine Control Module (ECM) communication circuit or a failure in the controller area network (CAN) data link system. This code specifically signals that the main ECM is not receiving proper communication signals from connected control modules, or there's a disruption in the machine's internal network communication.

This fault is critical for the PC750-7 because the CAN bus system coordinates communication between the engine controller, hydraulic control modules, and monitoring systems. When this network fails, the excavator cannot properly regulate engine performance, hydraulic functions, or display accurate operational data to the operator.

Common Symptoms

When Code E116 is active on your PC750-7, operators typically experience:

• Warning lights illuminated on the monitor panel, often accompanied by error messages indicating communication failure
• Intermittent or complete loss of gauge readings (fuel level, coolant temperature, hydraulic oil temperature)
• Engine derate mode activation, limiting machine power output to protect systems
• Erratic hydraulic response or inability to access certain work modes
• Diagnostic monitor displaying multiple simultaneous fault codes due to communication breakdown

Potential Causes

The most common technical causes for E116 on used PC750-7 excavators include:

• CAN bus wiring harness damage from rubbing against frame components, particularly near the engine bay and cab mounting points
• Corroded or loose connector pins at the ECM or junction box connections, especially on machines with high operating hours
• Failed ECM internal circuits due to voltage spikes, moisture intrusion, or age-related component degradation
• Damaged termination resistors in the CAN network causing signal reflection issues
• Faulty relay or power supply to the communication network creating intermittent voltage drops

How to Troubleshoot and Fix Code E116

Step 1: Visual Inspection Begin by thoroughly inspecting all wiring harnesses between the ECM and other control modules. On used excavators, check for harness wear at known friction points near the engine mounts and cab pivot areas. Examine all connector pins for corrosion, bent terminals, or moisture intrusion.

Step 2: Electrical Testing Using a digital multimeter, verify proper voltage supply to the ECM (typically 24V on this model). Check CAN-High and CAN-Low circuit resistance between communication modules—readings should show approximately 60 ohms with ignition off, indicating proper termination resistor function.

Step 3: Advanced Diagnostics Connect Komatsu KOMTRAX or compatible diagnostic software to monitor real-time CAN bus activity. Check for intermittent signal dropouts or missing data packets. Test termination resistors at network endpoints—replace if readings deviate from specifications.

Step 4: Component Replacement If wiring and connections test properly, suspect ECM internal failure. Before replacing the expensive controller on used equipment, verify all ground connections are clean and tight, as poor grounds frequently mimic ECM failures.

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Disclaimer: This guide provides general troubleshooting information. Always consult Komatsu service manuals and qualified diesel technicians for complex electrical diagnostics. Improper repairs may cause additional system damage.