What is Sany Excavator Fault Code P835?

Fault Code P835 indicates a malfunction in the Engine Speed Sensor Circuit or an invalid signal being received by the Engine Control Module (ECM). This code specifically relates to the crankshaft position sensor or engine speed sensor failing to provide consistent, reliable data to the ECM for proper engine timing and fuel injection control.

The engine speed sensor is critical for Sany excavators as it monitors crankshaft rotation speed and position, allowing the ECM to precisely control fuel injection timing, ignition events, and overall engine performance. When this sensor circuit fails or sends erratic signals, the ECM cannot accurately manage combustion cycles, leading to poor performance or complete shutdown. This is particularly problematic in used excavators where sensor degradation and wiring harness wear are common issues that compromise signal integrity.

Common Symptoms

When Code P835 is active, operators typically experience:

• Check Engine Light or malfunction indicator lamp illuminated on the instrument panel
• Engine cranks but fails to start or experiences extended cranking time before firing
• Rough idle, misfiring, or erratic engine RPM fluctuations during operation
• Sudden engine stalling or unexpected shutdowns, especially under load
• Loss of power or engine derate mode limiting machine performance to protect engine components

Potential Causes

The most common technical reasons for P835 on used Sany excavators include:

• Failed or degraded engine speed sensor due to heat exposure, vibration damage, or internal component wear
• Damaged wiring harness or connector corrosion at the sensor plug, especially where harnesses route near the engine block or exhaust components
• Intermittent electrical connections caused by loose connectors, corroded pins, or oil contamination in the sensor plug
• Damaged reluctor ring (tone wheel) on the crankshaft with missing teeth or debris accumulation
• ECM internal faults or software corruption affecting signal interpretation (less common)
• Inadequate sensor gap clearance due to improper installation or mounting bracket wear in older machines

How to Troubleshoot and Fix Code P835

Step 1: Visual Inspection Begin by locating the engine speed sensor (typically mounted on the engine block near the flywheel or crankshaft pulley). Inspect the sensor body for physical damage, oil leaks, or excessive heat discoloration. On used excavators, carefully examine the wiring harness for rubbing points, frayed insulation, or areas where the harness contacts hot engine surfaces or sharp edges.

Step 2: Connector and Electrical Testing Disconnect the sensor connector and inspect for corrosion, bent pins, or oil intrusion. Clean contacts with electrical contact cleaner if necessary. Using a digital multimeter, check sensor resistance (typically 200-1000 ohms depending on sensor type—consult service manual for exact specifications). Test harness continuity from sensor connector to ECM and check for shorts to ground.

Step 3: Signal and Gap Verification With the sensor reconnected, use Sany diagnostic software or a compatible scan tool to monitor live engine speed sensor data while cranking. The signal should show consistent AC voltage pulses (typically 0.5-5 volts AC). Verify the air gap between sensor tip and reluctor ring is within specification (usually 0.5-1.5mm). Remove the sensor and inspect the reluctor ring for damage or metallic debris buildup.

Step 4: Component Replacement and Verification If testing confirms sensor failure, replace with a genuine or OEM-equivalent engine speed sensor. For used machines, always replace the connector pigtail if corrosion is present, as this prevents recurring issues. After replacement, clear fault codes using diagnostic software, perform a cranking test, and road-test the machine under load to verify proper operation.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Sany service manual for your specific model and serial number. If you're uncomfortable performing electrical diagnostics, consult a qualified heavy equipment technician to prevent further damage or safety hazards.