What is Sany General Fault Code P358?

Fault Code P358 indicates a malfunction in the Engine Coolant Temperature (ECT) Sensor Circuit High Voltage condition. This diagnostic trouble code triggers when the Engine Control Module (ECM) detects an abnormally high voltage signal from the coolant temperature sensor, typically above 4.8 volts, suggesting an open circuit, damaged sensor, or wiring harness issue.

In Sany excavators, the ECT sensor plays a critical role in engine performance management by monitoring coolant temperature and relaying data to the ECM. This information directly affects fuel injection timing, idle speed control, and engine protection protocols. When P358 activates, the ECM may default to a predetermined temperature value, potentially causing inefficient combustion, increased emissions, and inadequate engine protection against overheating.

Common Symptoms

Operators experiencing Code P358 may notice:

• Check Engine Light or malfunction indicator illuminated on the instrument cluster
• Engine derate mode activated, limiting maximum RPM and hydraulic performance
• Hard starting conditions, especially during cold weather operation
• Rough idling or unstable engine speed at operating temperature
• Cooling fan running continuously at maximum speed regardless of actual engine temperature

Potential Causes

The most common technical causes for P358 in used Sany excavators include:

• Open circuit in ECT sensor wiring harness, often caused by chafing against the engine block or frame components near the thermostat housing
• Corroded or damaged connector pins at the sensor plug due to coolant leaks or moisture intrusion
• Failed coolant temperature sensor with internal open circuit (common after 5,000+ operating hours)
• ECM internal circuit damage affecting the sensor reference voltage supply
• Broken or severed ground wire specific to the sensor circuit

How to Troubleshoot and Fix Code P358

Step 1: Visual Inspection Locate the ECT sensor (typically installed near the thermostat housing on Sany engines). Inspect the wiring harness for obvious damage, worn insulation, or evidence of rubbing. On used excavators, check for coolant residue indicating leaks that may have damaged connectors. Disconnect the sensor and examine connector pins for corrosion or bent terminals.

Step 2: Electrical Testing Using a digital multimeter, test the sensor resistance. At room temperature (68°F/20°C), resistance should typically read 2,000-3,000 ohms. Check the reference voltage at the disconnected harness connector—it should read approximately 5 volts with the key on, engine off. If voltage is absent or incorrect, trace the signal wire back toward the ECM for breaks.

Step 3: Component Replacement If sensor resistance is out of specification or the harness shows voltage irregularities, replace the faulty component. For used machines, always apply dielectric grease to connector pins before reassembly to prevent future corrosion. Clear codes using Sany diagnostic software and verify proper operation through a heat cycle.

Disclaimer: This guide provides general troubleshooting information. Always consult factory service manuals and consider professional diagnostic services for complex electrical issues or if unfamiliar with high-voltage systems.