What is Sany SY245H Fault Code 27 (E327)?

Fault Code 27 (E327) on the Sany SY245H excavator indicates a Main Relief Valve Pressure Sensor Circuit Malfunction or abnormal hydraulic system pressure reading. This diagnostic trouble code (DTC) is triggered when the Electronic Control Unit (ECU) detects voltage signals from the main relief pressure sensor that fall outside the manufacturer's predetermined range (typically 0.5-4.5V).

This code is critical for the SY245H because the main relief pressure sensor monitors the hydraulic system's maximum operating pressure, typically set around 34.3 MPa (350 bar). When this sensor fails or provides erratic readings, the ECU cannot properly regulate hydraulic functions, potentially leading to component damage, reduced digging force, or unsafe operating conditions. On used Sany excavators, this code often appears due to sensor degradation or wiring harness issues common in machines with 3,000+ operating hours.

Common Symptoms

• Hydraulic function derate or reduced power across all circuits (boom, arm, bucket, swing)
• Warning light illumination on the instrument cluster, often accompanied by an audible alarm
• Erratic or sluggish hydraulic response, particularly during high-demand operations like heavy digging
• Intermittent error codes that appear and disappear, indicating loose connections or corroded terminals
• ECU entering limp mode, restricting machine operation to low-power settings to prevent system damage

Potential Causes

The most common technical failures triggering Code 27 on used SY245H excavators include:

• Pressure sensor failure due to internal diaphragm rupture or electronic component degradation (common after 5+ years)
• Wiring harness damage at known rub points near the main pump assembly or along the upper structure rotation path
• Corroded or loose connector pins at the sensor plug (4-pin Deutsch connector), especially on machines operated in wet/humid environments
• ECU voltage supply issues, including degraded grounds or 5V reference voltage irregularities
• Hydraulic contamination causing sensor port blockage or membrane coating
• Previous repair attempts using non-OEM sensors with incompatible resistance values (typically should be 0-5V output)

How to Troubleshoot and Fix Code 27 (E327)

Step 1: Visual Inspection and Connector Examination Begin by locating the main relief pressure sensor mounted on the main control valve body. Disconnect the sensor 4-pin connector and inspect for corrosion, bent pins, moisture intrusion, or oil contamination. On used excavators, check the wiring harness routing for evidence of chafing against the pump housing or chassis—a common failure point on SY245H models. Clean connectors with electrical contact cleaner and apply dielectric grease.

Step 2: Sensor Voltage and Resistance Testing Using a digital multimeter (DMM), perform a resistance check across the sensor terminals with the connector disconnected. The sensor should read approximately 250-350 ohms at room temperature (consult your specific service manual for exact specs). Next, reconnect the sensor and backprobe the harness with the ignition ON, engine OFF. Verify the 5V reference voltage from the ECU and check the signal wire voltage (should be 0.5-4.5V corresponding to pressure). Readings outside this range indicate sensor replacement is necessary.

Step 3: Harness Continuity and ECU Verification Test continuity between the sensor connector and the ECU pins (typically pins 23 and 24 on Sany ECUs) to identify open circuits or high-resistance connections exceeding 5 ohms. Inspect harness sections that pass through rotating joints or near heat sources. If harness integrity is confirmed and a new OEM-equivalent sensor still triggers the code, the ECU may require reflashing with Sany PC-E1 diagnostic software or replacement—a less common scenario requiring dealer-level tools.

For used excavators specifically: Before ordering parts, perform a hydraulic pressure calibration using diagnostic software, as incorrect baseline settings from previous repairs can false-trigger this code.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the official Sany service manual for your specific machine serial number and consider professional diagnostic services for complex electrical issues or ECU programming.