What is Hitachi Excavator Fault Code 00628-02P0601?

Fault Code 00628-02P0601 indicates an Internal Control Module Performance issue, specifically related to the Engine Control Module (ECM) detecting an internal processing error or memory fault within its own circuitry. This code signals that the ECM has identified a problem with its ability to properly execute control functions, process sensor data, or maintain correct internal communication between its microprocessors.

In Hitachi excavators, the ECM serves as the brain of the engine management system, controlling fuel injection timing, throttle response, emissions systems, and sensor monitoring. When this fault appears, the ECM has detected that its internal operations are not performing within manufacturer specifications. This is critical because ECM malfunctions can lead to improper engine control, unexpected shutdowns, or inability to start, directly impacting productivity and potentially causing secondary damage to engine components.

Common Symptoms

• Check Engine Light or Warning Lamp illuminated on the dashboard with possible engine derate mode activated
• Engine may enter limp mode, limiting RPM and hydraulic power output to protect against further damage
• Difficulty starting the engine or intermittent starting issues, particularly after the machine has been sitting
• Erratic engine behavior including rough idling, unexpected RPM fluctuations, or sudden loss of power during operation
• Complete engine shutdown in severe cases, with inability to restart until the fault is addressed

Potential Causes

The most common technical causes for Code 00628-02P0601 in used Hitachi excavators include:

• ECM internal hardware failure due to age, heat cycling, or component degradation (common in machines with 5,000+ operating hours)
• Corrupted ECM software or firmware caused by interrupted software updates, voltage spikes, or memory degradation
• Low or unstable battery voltage supplying insufficient power to the ECM during startup or operation
• Corroded or loose ECM power and ground connections, particularly at the main harness connector (a known wear point on older machines)
• Water intrusion or moisture contamination inside the ECM housing, common in excavators operating in wet or humid environments
• Voltage transients or electrical noise from failing alternators, starter motors, or damaged wiring harnesses affecting ECM operation

How to Troubleshoot and Fix Code 00628-02P0601

Step 1: Verify Battery and Charging System Begin by testing the battery voltage with a multimeter—it should read 12.6-12.8V with the engine off and 13.5-14.5V while running. Check all battery cable connections and clean any corrosion. Low or fluctuating voltage is a frequent culprit in used machines and can cause false ECM errors.

Step 2: Inspect ECM Connections and Harness Locate the ECM (typically mounted near the engine or under the cab) and thoroughly inspect the main harness connector. Look for corrosion, bent pins, moisture, or oil contamination in the connector. Check the ground connections at the ECM mounting bracket—poor grounds are especially common in older excavators. Examine the wiring harness for chafing, rubbing points, or damaged insulation where it routes near moving components or sharp edges.

Step 3: Perform ECM Software Check and Reprogramming Connect Hitachi diagnostic software (Dr. EX or equivalent dealer-level software) to verify the ECM firmware version. Attempt to clear the fault code and monitor for immediate return. If the code returns instantly without starting the engine, this indicates an internal ECM hardware fault. If codes clear successfully, perform an ECM reprogramming or firmware update as corrupted software can trigger this fault.

Step 4: Test ECM Power Supply With the multimeter, check voltage at the ECM power supply pins (consult service manual for pinout). Verify that the ECM receives constant 12V power and switched ignition power as specified. Voltage drop testing on power and ground circuits should show less than 0.2V drop under load.

Step 5: ECM Replacement Consideration If all electrical connections, power supply, and software checks are satisfactory but the code persists, the ECM likely has internal component failure and requires replacement. For used excavators, consider sourcing a remanufactured ECM or having your existing unit professionally rebuilt, as new ECMs can be cost-prohibitive. Ensure any replacement ECM is properly programmed with the correct machine parameters and software version.

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Disclaimer: This guide provides general troubleshooting information for Hitachi excavator fault codes. Always consult the manufacturer's service manual for your specific model and consider engaging a certified Hitachi technician or qualified diesel mechanic for complex ECM diagnostics and repairs. Improper ECM handling or installation may cause additional machine damage.