What is Sumitomo SH290-5 Fault Code 118?

Fault Code 118 on the Sumitomo SH290-5 excavator indicates a Pilot Pressure Sensor Circuit Malfunction or abnormal pilot pressure system voltage. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an electrical signal from the pilot pressure sensor that falls outside the manufacturer's specified voltage range (typically 0.5-4.5V).

The pilot pressure sensor is critical for the SH290-5's hydraulic control system, as it monitors the pressure generated when the operator moves the control levers. This sensor communicates with the ECM to modulate hydraulic flow and ensure precise implement control. When Code 118 activates, the machine's computerized control system cannot accurately read pilot pressure inputs, potentially affecting all hydraulic functions and operator safety.

Common Symptoms

When Fault Code 118 is active on your Sumitomo SH290-5, you may experience:

• Warning light illumination on the instrument cluster with simultaneous error code display
• Erratic or unresponsive hydraulic controls, particularly sluggish boom, arm, or bucket movements
• Complete loss of pilot control functions, forcing the machine into a safety shutdown mode
• Intermittent hydraulic response that worsens as the machine warms up or during extended operation
• Reduced engine RPM or automatic derate mode to protect hydraulic components

Potential Causes

The most common technical reasons for Code 118 on used SH290-5 excavators include:

• Pilot pressure sensor internal failure due to age, contamination, or electrical component degradation
• Damaged or corroded wiring harness connections at the sensor plug, especially where the harness routes near the operator's cab mount (known rub point)
• Shorted or open circuit in the sensor signal wire between the sensor and ECM
• Contaminated hydraulic pilot oil causing sensor membrane damage or inaccurate readings
• ECM voltage supply issues, including faulty 5V reference voltage output to the sensor
• Water intrusion into sensor connectors from damaged cab seals or improper washing procedures

How to Troubleshoot and Fix Code 118

Step 1: Visual Inspection Begin by locating the pilot pressure sensor (typically mounted on the main control valve near the operator's seat). Inspect the sensor body for physical damage, oil leaks, or contamination. Carefully examine the wiring harness and connector for corrosion, bent pins, or oil intrusion. On used excavators, check where the harness passes through the cab mounting area—this is a common wear point on SH290-5 models.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure the ECM's 5V reference voltage supply at the harness side (consult service manual for specific pin locations). You should read approximately 5.0V ±0.25V. Next, check sensor ground continuity to chassis ground (should be less than 1 ohm). Measure sensor internal resistance across signal and ground pins with the sensor disconnected (typical range: 200-5000 ohms depending on temperature).

Step 3: Sensor Signal Testing Reconnect the sensor and back-probe the signal wire while operating the pilot controls. The voltage should smoothly vary between approximately 0.8V (neutral) and 4.2V (full lever deflection). Erratic readings, voltage spikes, or frozen values indicate sensor failure. For used machines, temporarily swap with a known-good sensor before purchasing replacements.

Step 4: Harness and ECM Verification If sensor tests pass, inspect the entire harness length for internal wire breaks using a continuity tester while flexing the harness. Check ECM connector terminals for corrosion or looseness. On high-hour used excavators, consider checking hydraulic pilot oil quality—contamination can damage sensor internals even if electrical tests pass.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Sumitomo service manual for your specific machine serial number and software version. If you're uncomfortable performing electrical diagnostics, contact a certified Sumitomo technician to prevent further damage to expensive hydraulic or electronic components.