Sumitomo SH80-6B Fault Code P1664-2: Complete Diagnostic Guide

What is Sumitomo SH80-6B Fault Code P1664-2?

Fault Code P1664-2 indicates a hydraulic system sensor circuit malfunction, specifically related to the pump pressure sensor or its associated wiring harness. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormal voltage signal from the hydraulic pressure monitoring circuit, typically indicating values outside the manufacturer's specified range of 0.5-4.5 volts.

This code is critical for the SH80-6B because the pump pressure sensor directly influences the machine's load-sensing hydraulic system. When this sensor fails or sends erratic signals, the ECM cannot properly regulate hydraulic pump output, potentially leading to reduced performance, inefficient fuel consumption, or complete hydraulic system derate to protect components from damage.

Common Symptoms

When Code P1664-2 is active on your Sumitomo SH80-6B, operators typically experience:

• Intermittent or constant hydraulic power loss, particularly during combined functions (boom and swing simultaneously)
• Warning lamp illumination on the instrument cluster, often accompanied by a diagnostic code display
• Erratic hydraulic response where controls feel sluggish or overly sensitive without consistency
• Automatic engine derate to approximately 1,500 RPM in severe cases to prevent hydraulic system damage
• Increased fuel consumption due to the pump running at maximum displacement when sensor feedback is lost

Potential Causes

The most common technical failures causing P1664-2 on used SH80-6B excavators include:

• Pressure sensor internal failure due to contaminated hydraulic fluid entering the sensor diaphragm over time
• Corroded or damaged connector pins at the sensor harness connection point near the hydraulic pump
• Wiring harness chafing at known rub points where the sensor cable routes along the pump mounting bracket
• ECM internal circuit damage from voltage spikes during jump-starting or welding operations
• Contaminated hydraulic oil causing sensor membrane degradation (common in machines with inconsistent maintenance history)
• Water intrusion into the sensor connector from pressure washing or working in wet conditions

How to Troubleshoot and Fix Code P1664-2

Step 1: Visual Inspection and Connector Check Begin by locating the hydraulic pressure sensor mounted on the main hydraulic pump body. Disconnect the sensor's electrical connector and inspect for corrosion, bent pins, or oil contamination. On used excavators, pay special attention to the connector seal—deteriorated seals allow moisture entry. Clean connections with electrical contact cleaner and apply dielectric grease before reconnection.

Step 2: Sensor Circuit Testing Using a digital multimeter (DVOM), perform a voltage supply test. With the ignition on and sensor disconnected, check for 5-volt reference voltage at the harness connector. Next, test sensor ground continuity (should read less than 1 ohm to chassis ground). Measure sensor output voltage while manually pressurizing the hydraulic system—it should sweep smoothly from approximately 0.5V (low pressure) to 4.5V (high pressure). Erratic readings indicate sensor failure.

Step 3: Wiring Harness and ECM Verification Inspect the entire sensor harness from connector to ECM, especially where it passes near rotating components or sharp edges. On the SH80-6B, the harness routing near the swing motor is a known wear point. Check for harness resistance (should be under 5 ohms total). If sensor and wiring test correctly but the code persists, ECM reprogramming or replacement may be necessary—consult Sumitomo diagnostic software for parameter verification.

Important for Used Equipment: Before replacing the pressure sensor, verify hydraulic oil quality and change filters if maintenance history is unknown. Contaminated oil often damages new sensors within hours of installation.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Sumitomo service manual for your specific machine serial number and consider professional assistance for complex electrical diagnostics or ECM programming.