Komatsu PC1250-8R Fault Code E10CA757: Complete Diagnostic Guide

What is Komatsu PC1250-8R Fault Code E10CA757?

Fault Code E10CA757 indicates a communication error between the Engine Controller (ECM) and the Hydraulic Pump Controller (HPC) on the Komatsu PC1250-8R excavator. This code specifically flags a CAN bus communication failure or timeout between these two critical control modules.

The Controller Area Network (CAN bus) serves as the digital nervous system for this machine, allowing the ECM and HPC to coordinate engine power output with hydraulic demand. When communication breaks down, the excavator cannot properly match engine speed to hydraulic load requirements, severely impacting performance and fuel efficiency. On the PC1250-8R, this coordination is essential for the machine's advanced load-sensing hydraulic system to function correctly.

Common Symptoms

When Code E10CA757 is active, operators typically experience:

• Warning light illumination on the monitor panel with error message display
• Engine derating or failure to reach maximum RPM under load
• Sluggish hydraulic response during combined functions (swing + boom operations)
• Erratic engine RPM fluctuations when operating hydraulic controls
• Increased fuel consumption due to improper engine-pump matching

Potential Causes

The most common technical causes for this fault code include:

• CAN bus wiring damage at known rub points near the engine mounting brackets and along the main harness routing behind the cab
• Corroded or loose connector contacts at the ECM (located behind the cab) or HPC (mounted on the hydraulic pump)
• Controller power supply issues, particularly low voltage to the HPC during cranking or operation
• ECM or HPC internal failure, more common in high-hour used machines (8,000+ hours)
• Aftermarket modifications or improper wiring repairs that created resistance or signal interference

How to Troubleshoot and Fix Code E10CA757

Step 1: Visual Harness Inspection Begin by inspecting the CAN bus harness (typically yellow or orange twisted pair wiring) from the ECM to the HPC. Focus on areas where the harness passes near moving components, engine mounts, and through bulkhead connectors. On used excavators, look specifically for chafed insulation, pinched wires, or oil contamination that degrades wire integrity.

Step 2: Connector and Termination Check Disconnect both the ECM connector (usually a large multi-pin Deutsch connector) and the HPC connector. Inspect pins for corrosion, bent contacts, or moisture intrusion. Use electrical contact cleaner and verify all pins are properly seated. Check CAN bus termination resistors—you should measure approximately 60 ohms resistance between CAN-H and CAN-L with both controllers disconnected.

Step 3: Voltage and Signal Testing Using a digital multimeter, verify the HPC receives proper supply voltage (typically 24V DC). With the key on, use Komatsu KOMTRAX diagnostic software or a compatible CAN bus analyzer to monitor real-time communication packets. Check for signal voltage on CAN-H (approximately 3.5V) and CAN-L (approximately 1.5V) during normal operation.

Step 4: Controller Testing If wiring and connections test correctly, the fault likely resides in one of the controllers. On high-hour used machines, ECM capacitor degradation is common. Consider swapping controllers with a known-good unit for definitive diagnosis before purchasing expensive replacements.

Disclaimer: This guide provides general diagnostic procedures. Always consult the official Komatsu service manual for your specific machine serial number and consider professional technician assistance for complex electrical diagnostics.