What is Sany SY245/265H Fault Code 70?

Fault Code 70 on the Sany SY245/265H excavator indicates a malfunction in the engine speed sensor circuit or an abnormal signal from the crankshaft position sensor. This code is generated when the Mitsubishi Heavy Industries engine control module (ECM) detects an inconsistent or missing signal from the sensor responsible for monitoring engine RPM and crankshaft positioning.

The crankshaft position sensor is critical for proper fuel injection timing, ignition sequencing, and overall engine synchronization. When this sensor fails or sends erratic signals, the ECM cannot accurately control combustion events, leading to performance degradation or complete engine shutdown. On used excavators, this fault often stems from sensor degradation, wiring harness damage, or connector corrosion—common issues in machines with thousands of operating hours in harsh environments.

Common Symptoms

When Fault Code 70 is active, operators typically experience:

• Engine cranks but fails to start or starts with extreme difficulty
• Sudden engine stalling during operation, especially under load
• Erratic engine RPM fluctuations or rough idling
• Check engine light illuminated on the instrument panel
• Loss of engine power or failure to reach full throttle response

Potential Causes

The most common technical reasons for Code 70 appearing on used Sany SY245/265H excavators include:

• Crankshaft position sensor failure due to heat exposure or internal component breakdown
• Damaged or frayed wiring harness near the sensor, particularly where cables route close to the engine block or exhaust manifold
• Corroded or loose electrical connectors at the sensor or ECM connection points
• Contaminated sensor face from oil leaks, metal shavings, or debris accumulation
• ECM software glitches or internal ECM failure (less common but possible in high-hour machines)
• Improper air gap between the sensor and crankshaft reluctor ring due to mounting bracket wear

How to Troubleshoot and Fix Code 70

Step 1: Visual Inspection Begin by locating the crankshaft position sensor (typically mounted on the engine block near the flywheel housing). Inspect the wiring harness for obvious damage, abrasion points where cables contact metal surfaces, or oil contamination. Check all connector pins for corrosion, bent terminals, or moisture intrusion—common in used equipment.

Step 2: Electrical Testing Using a digital multimeter, test the sensor's resistance. Mitsubishi sensors typically read between 150-300 ohms (consult your service manual for exact specifications). Check for continuity in the wiring from sensor to ECM. Measure voltage supply at the sensor connector (usually 5V or 12V reference voltage from the ECM).

Step 3: Sensor Gap and Cleaning Remove the sensor and inspect the reluctor ring on the crankshaft for damage or debris buildup. Clean the sensor face with electrical contact cleaner. Verify the air gap specification (typically 0.5-1.5mm) and reinstall with proper torque.

Step 4: Component Replacement If testing reveals sensor failure, replace with an OEM or high-quality aftermarket crankshaft position sensor. For used excavators, always apply dielectric grease to connectors during reassembly to prevent future corrosion. Clear the fault code using Mitsubishi MUT-III diagnostic software or compatible scan tool and perform a test run.

Professional Disclaimer: While these steps cover common diagnostic procedures, complex electrical issues may require factory-level diagnostic equipment and expertise. Always consult a certified Mitsubishi or Sany technician for persistent faults or if you're unfamiliar with high-voltage electrical systems.