What is Sany General Fault Code H058?

Fault Code H058 indicates a malfunction in the hydraulic oil temperature sensor circuit or an abnormal temperature reading beyond the safe operating range. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects either an open circuit, short circuit, or an implausible signal from the hydraulic oil temperature sensor.

In Sany excavators, maintaining proper hydraulic fluid temperature (typically 50-80°C / 122-176°F) is critical for optimal viscosity, system efficiency, and component longevity. When H058 activates, the ECM may limit machine performance to prevent catastrophic hydraulic system damage, making this code a high-priority diagnostic concern for operators and mechanics alike.

Common Symptoms

When fault code H058 is active, operators typically experience:

• Dashboard warning light illuminated (hydraulic system or general malfunction indicator)
• Reduced hydraulic performance including slower cycle times and weak digging force
• ECM-initiated derate mode limiting engine RPM or hydraulic flow to protect the system
• Erratic temperature gauge readings or temperature display showing implausible values (e.g., -40°C or 200°C+)
• Intermittent code activation especially during cold starts or after extended operation in used machines with degraded wiring

Potential Causes

The most common technical causes for H058 in used Sany excavators include:

• Failed hydraulic oil temperature sensor due to internal element degradation or contamination exposure
• Damaged wiring harness particularly at known rub points near the hydraulic tank mounting brackets
• Corroded or loose connector pins at the sensor plug (common in machines exposed to moisture or mud)
• ECM internal fault or software calibration issue (less common but possible in older units)
• Contaminated hydraulic oil causing actual overheating that triggers legitimate sensor readings
• Poor ground connection at the sensor circuit return path

How to Troubleshoot and Fix Code H058

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor (typically mounted on the hydraulic tank or main return line). Inspect the wiring harness for obvious damage, abrasion, or oil contamination. Check the connector for corrosion, bent pins, or moisture intrusion—particularly critical in used excavators with years of field exposure.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance at ambient temperature (typically 2,000-3,000 ohms at 20°C, but verify against Sany specifications). Test the harness continuity from the sensor connector back to the ECM. Check for short circuits to ground (should read infinite resistance) and verify supply voltage (usually 5V reference from ECM).

Step 3: Component Replacement and Verification If the sensor resistance is out of specification or the wiring shows damage, replace the faulty component. For used machines, always apply dielectric grease to connector pins before reassembly to prevent future corrosion. Clear the fault code using Sany diagnostic software or a compatible scan tool, then operate the machine through a complete warm-up cycle to verify the repair.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Sany service manual for your specific model and consider professional diagnostic assistance for complex electrical issues or if you lack proper testing equipment.