Komatsu PC1250SP-8R Fault Code E10CA757: Meaning and Fix

What is Komatsu PC1250SP-8R Fault Code E10CA757?

Fault Code E10CA757 indicates a communication error between the Engine Control Module (ECM) and the Hydraulic Control Module (HCM) on the Komatsu PC1250SP-8R excavator. This code specifically signals a CAN bus communication failure or data transmission interruption between these critical control systems.

The PC1250SP-8R relies on continuous communication between the ECM and HCM to coordinate engine power output with hydraulic demand. When this communication link fails, the machine cannot properly synchronize engine speed with hydraulic pump requirements, severely compromising operational efficiency. This is particularly critical on this model, as the hydraulic pump control system depends on real-time engine data to optimize fuel consumption and prevent overloading during heavy excavation cycles.

Common Symptoms

When Code E10CA757 is active, operators typically experience:

• Engine derate mode activated, limiting machine to 70-80% power output
• Hydraulic system sluggishness with noticeably slower cycle times on boom, arm, and bucket functions
• Multiple warning lights illuminated on the monitor panel, including the engine warning lamp
• Intermittent loss of hydraulic power during operation, particularly under heavy loads
• Erratic engine RPM fluctuations when engaging hydraulic functions

Potential Causes

The most common technical causes for E10CA757 on used PC1250SP-8R excavators include:

• CAN bus wiring harness damage at known rub points near the main frame pivot and along the upper structure
• Corroded or moisture-contaminated connectors between ECM and HCM, especially in machines operating in wet or coastal environments
• Failed terminating resistor on the CAN network (120-ohm resistor deterioration)
• ECM or HCM module internal failure, more common in high-hour machines (8,000+ hours)
• Voltage supply issues to either control module due to failing relays or poor ground connections
• Software version mismatch between ECM and HCM after previous repairs or module replacements

How to Troubleshoot and Fix Code E10CA757

Step 1: Initial Visual Inspection Begin by inspecting the wiring harness routing between the ECM (located behind the operator cab) and the HCM (mounted near the hydraulic pumps). On used excavators, check specifically where harnesses pass through bulkheads and near the swing bearing—common wear points. Look for chafed insulation, pinched wires, or visible damage.

Step 2: Connector and Termination Check Disconnect and inspect all CAN bus connectors for corrosion, bent pins, or moisture intrusion. Clean with electrical contact cleaner and apply dielectric grease. Using a digital multimeter, verify the terminating resistor reads approximately 60 ohms between CAN-High and CAN-Low lines with both modules disconnected (two 120-ohm resistors in parallel).

Step 3: Voltage and Communication Testing With ignition on, measure supply voltage at both ECM and HCM—should read 24V DC (±2V). Using Komatsu KOMTRAX or diagnostic software, monitor live CAN bus traffic. Check for communication dropouts or error frames. Test resistance on CAN-High and CAN-Low wires—should read 120 ohms end-to-end with modules disconnected.

Step 4: Module Verification and Replacement If wiring and connections test good, suspect module failure. For used machines, ECM/HCM failures often result from vibration damage or thermal cycling. Swap modules with known-good units if available, or send for professional testing before purchasing expensive replacements.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine serial number and seek professional diagnostic assistance for complex electrical issues. Improper repairs may cause additional damage or safety hazards.