What is Komatsu PC200-7 Fault Code E-18?

Fault Code E-18 on the Komatsu PC200-7 excavator indicates a malfunction in the pump discharge pressure sensor circuit. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormal voltage signal from the pressure sensor that monitors the main hydraulic pump's discharge pressure.

The pump discharge pressure sensor is critical for the PC200-7's load-sensing hydraulic system. It provides real-time feedback to the ECM, allowing the machine to optimize pump output, regulate flow control, and protect the hydraulic system from overpressure conditions. When this sensor circuit fails, the excavator cannot accurately monitor hydraulic demand, potentially leading to reduced performance and fuel efficiency.

Common Symptoms

When Code E-18 is active on your Komatsu PC200-7, operators typically experience:

• Warning light illuminated on the monitor panel, often accompanied by an audible alarm
• Reduced hydraulic power during digging, lifting, or swinging operations
• Sluggish machine response to joystick commands, particularly under heavy loads
• Erratic boom or arm movement due to inconsistent pump flow regulation
• Engine derate mode where the ECM limits engine RPM to protect hydraulic components

Potential Causes

The most common technical reasons for E-18 on used PC200-7 excavators include:

• Faulty pump discharge pressure sensor due to internal component wear or contamination from hydraulic fluid degradation
• Damaged wiring harness near the main pump area where vibration and heat cause insulation breakdown
• Corroded or loose electrical connectors at the sensor or ECM interface points
• Short circuit or open circuit in the sensor signal wire, common at harness routing points near the pump
• Failed ECM (rare, but possible in high-hour machines with electrical system history)
• Low voltage supply to the sensor from degraded power supply circuits

How to Troubleshoot and Fix Code E-18

Step 1: Visual Inspection Begin by locating the pump discharge pressure sensor mounted on the main hydraulic pump. Inspect the sensor body for physical damage, oil contamination on electrical connections, and corroded terminals. On used excavators, check the wiring harness for rubbing against the pump housing or frame—a common wear point on the PC200-7.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure the supply voltage (should be approximately 5 volts with ignition on). Check sensor resistance according to Komatsu specifications (typically 200-400 ohms at room temperature). Test the signal wire for continuity from sensor to ECM connector pin and check for shorts to ground.

Step 3: Diagnostic Software Analysis Connect Komatsu diagnostic software (KOMTRAX or aftermarket compatible tool) to read real-time sensor values. Compare actual pressure readings against specifications during machine operation. An erratic signal or flat-line reading confirms sensor failure. For used machines, inspect connector pins for "green corrosion" commonly found in older PC200-7 models stored outdoors.

Step 4: Component Replacement If the sensor tests faulty, replace with a genuine Komatsu pressure sensor (Part No. 7861-93-1651 or equivalent). Clean all connector contacts with electrical contact cleaner before installation. For harness damage, repair using heat-shrink connectors and protect with split loom tubing. Clear codes with diagnostic software and perform a functional test under load.

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Disclaimer: This guide provides general troubleshooting information. Always consult the Komatsu PC200-7 service manual and qualified heavy equipment technicians for repairs involving hydraulic and electrical systems. Improper diagnosis can lead to further damage or safety hazards.