What is Sumitomo SH220LC-6 Fault Code 697?

Fault Code 697 on the Sumitomo SH220LC-6 excavator indicates a hydraulic oil temperature sensor circuit malfunction or an abnormal hydraulic oil temperature reading. This code is triggered when the Electronic Control Module (ECM) detects voltage signals outside the normal operating range from the hydraulic oil temperature sensor, or when the sensor reports temperatures that exceed safe operating limits.

This fault is critical for the SH220LC-6 because hydraulic oil temperature directly affects system viscosity, component lubrication, and seal integrity. The hydraulic system operates optimally between 50-80°C (122-176°F). When the ECM cannot accurately monitor oil temperature due to sensor circuit issues, it cannot protect the hydraulic pump, motors, and control valves from thermal damage. In used excavators, this code often appears after years of thermal cycling have degraded sensor components or wiring insulation.

Common Symptoms

• Hydraulic performance warning light illuminated on the instrument cluster, sometimes accompanied by an audible alarm
• Reduced hydraulic response or sluggish operation as the ECM may activate a protective derate mode limiting pump output
• Inaccurate temperature gauge readings showing either extremely high, extremely low, or erratic fluctuating values
• Hydraulic system overheating without corresponding warning if the sensor has failed in an open circuit condition
• Intermittent code activation that correlates with machine vibration or specific boom/arm positions (indicating wiring harness issues)

Potential Causes

• Hydraulic oil temperature sensor failure due to internal element degradation, especially common in machines with 8,000+ operating hours
• Damaged or corroded wiring harness connections at the sensor plug, often caused by hydraulic oil contamination or moisture intrusion in the tank area
• Chafed or pinched sensor wires where the harness routes near the hydraulic tank mounting brackets—a known wear point on SH220LC-6 models
• Corroded or loose ground connections affecting the sensor signal circuit reference voltage
• Actual hydraulic oil overheating due to restricted oil cooler, low oil level, or failing cooling fan (triggering legitimate high-temperature readings)
• ECM internal faults affecting the analog input circuit (rare, but possible in older machines)

How to Troubleshoot and Fix Code 697

Step 1: Visual Inspection and Initial Checks Begin by inspecting the hydraulic oil temperature sensor located on the hydraulic oil tank. Check the connector for corrosion, oil contamination, or pushed-back pins. On used excavators, this connector frequently shows green corrosion from condensation. Disconnect the sensor and inspect both male and female terminals. Clean with electrical contact cleaner and apply dielectric grease before reconnection.

Step 2: Sensor Resistance Testing Using a multimeter set to resistance mode, measure the sensor's resistance. Disconnect the sensor from the harness and measure across its terminals. Compare readings against Sumitomo specifications (typically 2,000-3,000 ohms at 20°C, decreasing to 200-300 ohms at 80°C for NTC-type sensors). If readings are infinite (open circuit) or near zero (short circuit), replace the sensor. For used machines, also submerge the sensor in heated oil to verify resistance changes predictably with temperature.

Step 3: Wiring Harness Continuity and Voltage Checks Check harness continuity from the sensor connector back to the ECM. Measure resistance on both signal and ground wires—should be less than 5 ohms. Inspect the harness routing near the tank mounting area and swing bearing, where abrasion commonly occurs on the SH220LC-6. With the sensor disconnected and ignition on, measure reference voltage at the harness connector (typically 5V from the ECM). If voltage is absent or incorrect, trace wiring for breaks or check ECM power supply circuits.

Step 4: Verify Actual Hydraulic Temperature Before concluding sensor failure, verify actual hydraulic oil temperature using an infrared thermometer on the tank surface and oil cooler. If oil is genuinely overheating (above 90°C/194°F), investigate cooling system issues: check oil cooler for debris blockage, verify cooling fan operation, inspect hydraulic oil level, and examine pump case drain flow for internal pump wear.

Step 5: Clear Code and Monitor After repairs, clear the fault code using Sumitomo diagnostic software or by disconnecting the battery negative terminal for 30 seconds. Operate the machine through normal work cycles while monitoring oil temperature. On used excavators with intermittent codes, secure all harness routing with new zip ties and inspect after 10 operating hours to ensure the fix holds.

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Disclaimer: This guide provides general troubleshooting information for Sumitomo SH220LC-6 excavators. Hydraulic and electrical systems can be hazardous. Always consult the manufacturer's service manual and consider professional diagnosis for complex issues, especially on used equipment where multiple wear-related factors may contribute to fault codes.