What is Komatsu PC450-7 Fault Code E957?

Fault Code E957 on the Komatsu PC450-7 indicates a malfunction in the KOMTRAX communication system, specifically a communication error between the machine's Engine Control Module (ECM) and the KOMTRAX telematics unit. This code signals that the machine's remote monitoring system cannot properly transmit or receive operational data, which is critical for fleet management and diagnostic capabilities.

The KOMTRAX system is Komatsu's proprietary telematics technology that monitors machine location, operating hours, fuel consumption, and diagnostic trouble codes in real-time. On the PC450-7, this system relies on a stable CAN bus network connection between the ECM, hydraulic controller, and the KOMTRAX module. When communication fails, Code E957 triggers, potentially leaving operators without critical remote monitoring capabilities. While this fault typically doesn't affect immediate machine operation, it compromises preventive maintenance scheduling and can mask underlying electrical issues common in used excavators.

Common Symptoms

• KOMTRAX indicator light illuminated or flashing on the monitor panel
• Loss of remote monitoring data transmission to fleet management systems
• Inability to retrieve machine hours, fuel data, or GPS location remotely
• Intermittent communication warnings appearing on the multi-function display
• In some cases, simultaneous fault codes related to CAN bus communication failures

Potential Causes

The most common causes of E957 on used PC450-7 excavators include:

• Corroded or damaged wiring harness connections between the ECM and KOMTRAX module, particularly at connector points behind the cab where moisture intrusion is common
• Failed KOMTRAX antenna or damaged antenna cable, especially on machines operated in harsh environments
• Loose or corroded ground connections specific to the KOMTRAX power supply circuit
• ECM software version incompatibility with the KOMTRAX unit after aftermarket ECM replacements
• Damaged CAN bus terminating resistors or short circuits in the communication network
• Battery voltage irregularities causing intermittent module resets (common in aging electrical systems)

How to Troubleshoot and Fix Code E957

Step 1: Visual Inspection of Harness and Connectors Start by inspecting the wiring harness running from the ECM (located behind the operator's seat) to the KOMTRAX unit (typically mounted under the cab). Check for chafing points where the harness passes through the cab mounting area—this is a known wear point on used PC450-7 machines. Clean all connector pins with electrical contact cleaner and verify no corrosion or bent pins exist.

Step 2: Verify Power Supply and Ground Circuits Using a digital multimeter, check for proper voltage at the KOMTRAX module connector. You should read 24V DC at the power pins with the key switch on. Test ground circuit resistance—it should read less than 1 ohm to chassis ground. On used machines, corrosion at ground terminals is extremely common and often the root cause.

Step 3: Test CAN Bus Communication Connect Komatsu diagnostic software (KESS or authorized equivalent) to the diagnostic port. Monitor live CAN bus data while the machine is running. Check for proper terminating resistor values (should read approximately 60 ohms across the CAN-H and CAN-L lines). If readings are unstable or out of range, inspect harness continuity.

Step 4: Inspect KOMTRAX Antenna and Module Physically inspect the KOMTRAX antenna mounting location for damage or water intrusion. Test the antenna cable for continuity and verify proper resistance values. If previous repairs were made to the machine's electrical system, ensure no aftermarket components are interfering with the communication network.

Step 5: Software and Module Testing Verify the ECM software version is compatible with the installed KOMTRAX unit using Komatsu diagnostic tools. Consider performing a module reset procedure through the diagnostic software. If all electrical checks pass but communication fails, the KOMTRAX module itself may require replacement—common on machines with 8,000+ operating hours.

Important Note: Always consult Komatsu service manuals specific to your machine's serial number range and consider professional diagnostic services when dealing with communication network issues. Improper repairs to CAN bus systems can cause cascading electrical failures.