What is Hitachi ZX240-5A Fault Code P1655(10010-2)?

Fault Code P1655(10010-2) on the Hitachi ZX240-5A excavator indicates a communication error or malfunction in the Engine Control Module (ECM) to Machine Control Module (MCM) data link circuit. This code specifically signals that the ECM is detecting abnormal voltage levels, intermittent signal interruption, or complete communication failure with the machine's central controller system.

This fault is critical because the ECM and MCM must maintain constant communication to coordinate engine performance with hydraulic demands, travel speed control, and implement functions. When this data link fails, the excavator cannot properly regulate power output or respond to operator commands efficiently. On the ZX240-5A model, this communication runs through a dedicated CAN bus network that integrates all electronic systems, making this code a priority diagnostic concern that can severely impact machine productivity.

Common Symptoms

• Engine derating or limited RPM range, with the machine refusing to reach full power output regardless of throttle position
• Intermittent or complete hydraulic function loss, particularly affecting swing speed, boom response, or travel controls
• Warning lamp illumination on the monitor panel, often accompanied by error messages indicating "communication error" or "system malfunction"
• Erratic instrument cluster behavior, including gauge fluctuations, blank displays, or inconsistent readings
• Engine stalling at idle or under load, particularly when multiple hydraulic functions are engaged simultaneously

Potential Causes

The most common technical failures triggering P1655(10010-2) on used ZX240-5A excavators include:

• Corroded or damaged wiring harness connections between the ECM and MCM, especially at connector points near the battery box where exposure to moisture and vibration is highest
• Broken or frayed CAN bus wiring, particularly in harness sections routed along the engine bay firewall where rubbing against metal edges occurs over thousands of operating hours
• Failed ECM or MCM ground connections, often caused by loose mounting bolts or corrosion buildup on grounding terminals
• ECM or MCM internal circuit board failure due to age, moisture intrusion through damaged seals, or voltage spikes from electrical system issues
• Damaged shielding on CAN bus cables, allowing electromagnetic interference from the starter motor, alternator, or hydraulic solenoids to corrupt data transmission

How to Troubleshoot and Fix Code P1655(10010-2)

Step 1: Visual Inspection of Communication Harness Begin by physically inspecting the entire wiring harness between the ECM (located on the engine) and the MCM (typically mounted in the cab electrical compartment). On used excavators, pay special attention to harness routing points where cables contact metal edges, particularly near the engine mounting area. Check all connectors for corrosion, bent pins, or moisture intrusion—these are extremely common failure points on machines with 5,000+ operating hours.

Step 2: Test CAN Bus Circuit Resistance and Continuity Using a digital multimeter, disconnect both ECM and MCM connectors and measure resistance across the CAN-High and CAN-Low wires. You should read approximately 60 ohms between these two wires with both modules disconnected (this represents the terminating resistors at each end of the bus). Check continuity on each individual wire from ECM to MCM—resistance should be less than 5 ohms. Any readings outside these parameters indicate wiring damage or poor connections.

Step 3: Verify Power Supply and Ground Integrity Measure voltage at the ECM power supply pin (consult Hitachi service manual for exact pin location) with the key in the ON position—you should read battery voltage (approximately 24V for this model). Test the ground circuit by measuring voltage drop between the ECM ground pin and the battery negative terminal while cranking the engine; readings above 0.2 volts indicate poor grounding requiring terminal cleaning or cable replacement.

Step 4: Utilize Hitachi Diagnostic Software Connect Hitachi Dr. EX diagnostic software via the machine's diagnostic port to monitor real-time CAN bus communication activity. The software will show communication packet transmission status and help isolate whether the fault originates from the ECM or MCM side. For used excavators without recent software updates, verify the ECM firmware version—outdated software can cause communication protocol mismatches.

Step 5: Address Common Used Machine Issues Before replacing expensive modules, address wear-related issues common to older ZX240-5A excavators: apply dielectric grease to all harness connectors, replace any chafed harness sections with proper protective sleeving, and ensure all grounding points are cleaned to bare metal with proper torque applied (typically 10-15 ft-lbs for ground terminals).

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Disclaimer: This guide provides general diagnostic information for experienced technicians. Always consult the official Hitachi service manual for your specific serial number range and consider professional diagnostic support for complex electrical issues. Improper troubleshooting can cause additional system damage.