What is Komatsu PC220-8 Fault Code E-27?

Komatsu PC220-8 Fault Code E-27 indicates a malfunction in the hydraulic oil temperature sensor circuit. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormal voltage reading from the hydraulic oil temperature sensor, typically indicating an open circuit, short circuit, or sensor failure.

The hydraulic oil temperature sensor is critical for the PC220-8's performance management system. It monitors hydraulic fluid temperature and sends voltage signals to the ECM, which uses this data to prevent overheating, optimize pump output, and protect hydraulic components. When Code E-27 activates, the machine may enter a protective derate mode to prevent potential damage to hydraulic pumps, motors, and seals.

Common Symptoms

When Code E-27 is active on your Komatsu PC220-8, you may experience:

• Hydraulic oil temperature warning light illuminated on the monitor panel
• Machine entering reduced power mode or limiting hydraulic functions
• Inaccurate or blank hydraulic temperature readings on the display
• Delayed hydraulic response or slower cycle times as the ECM applies conservative operating parameters
• Audible warning alarm accompanying the fault code display

Potential Causes

The most common technical causes for E-27 on used PC220-8 excavators include:

• Faulty hydraulic oil temperature sensor due to internal sensor element degradation or thermal cycling failures
• Damaged or corroded wiring harness connections at the sensor plug (common wear point near hydraulic tank)
• Broken or pinched sensor wiring along the harness routing from tank to ECM, especially at frame mounting points
• Corroded sensor terminals caused by moisture intrusion in older machines with compromised sealing
• ECM internal circuit failure (rare, but possible on high-hour machines)
• Intermittent ground connection issues at sensor mounting location

How to Troubleshoot and Fix Code E-27

Step 1: Visual Inspection Begin by inspecting the hydraulic oil temperature sensor located on the hydraulic tank. Check the sensor body for physical damage, oil leaks around the threads, and examine the connector pins for corrosion, bent terminals, or oil contamination. On used excavators, pay special attention to harness routing where cables may rub against frame members or hydraulic lines.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to check sensor resistance. The sensor should typically read 250-350 ohms at 68°F (20°C) (consult your PC220-8 service manual for exact specifications). Test the wiring harness for continuity from the sensor connector back to the ECM. Check for short circuits to ground by measuring resistance between each wire and chassis ground (should read infinite resistance/open circuit).

Step 3: Voltage Supply Check With the ignition on and sensor disconnected, measure voltage at the harness connector. You should see approximately 5 volts on the signal wire from the ECM. If voltage is absent, trace the harness for breaks or check ECM power supply circuits and ground connections.

Step 4: Sensor Replacement and Verification If testing confirms sensor failure, replace with a genuine Komatsu hydraulic oil temperature sensor (Part #7861-93-3520 or equivalent). Apply thread sealant rated for hydraulic systems, torque to specification, and ensure the connector is fully seated with the locking tab engaged. Clear the code using Komatsu diagnostic software (KOMTRAX) or a compatible diagnostic tool, then run the machine through operating temperature cycles to verify the repair.

Critical Note for Used Equipment: Before replacing the sensor, thoroughly inspect all connectors and harness sections for wear patterns common in high-hour PC220-8 machines, particularly where harnesses pass near the swing bearing and along the upper structure.

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Disclaimer: This guide provides general troubleshooting information for Code E-27. Always consult your Komatsu PC220-8 service manual for model-specific specifications and procedures. If you lack proper diagnostic equipment or experience with electrical systems, consult a certified Komatsu technician to avoid misdiagnosis or additional damage.