What is Sumitomo Excavator Fault Code P0335?

Fault Code P0335 indicates a Crankshaft Position Sensor "A" Circuit Malfunction. This code triggers when the Engine Control Module (ECM) detects an intermittent or absent signal from the crankshaft position sensor (CKP sensor), which monitors the rotational speed and exact position of the crankshaft.

In Sumitomo excavators equipped with diesel engines, the CKP sensor is critical for precise fuel injection timing and ignition sequencing. Without accurate crankshaft position data, the ECM cannot properly synchronize engine operations, leading to performance degradation or complete shutdown. This code is particularly serious because the sensor provides real-time data that directly affects combustion efficiency and engine reliability—essential for demanding excavation work.

Common Symptoms

Operators may experience the following issues when Code P0335 is active:

• Hard starting or no-start conditions, especially during cold starts or after the machine has been sitting idle
• Engine stalling at idle or during low-load operation, with intermittent power loss
• Rough idling with noticeable vibration or uneven engine running
• Check Engine Light (CEL) illuminated on the instrument panel, possibly with additional warning indicators
• Reduced engine power or failure to reach normal operating RPM under load

Potential Causes

Several factors commonly trigger P0335 in used Sumitomo excavators:

• Faulty crankshaft position sensor due to internal component degradation, heat exposure, or mechanical failure
• Damaged or corroded wiring harness and connectors, particularly at flex points near the engine block where vibration causes wire fraying
• Worn or broken reluctor ring (tone wheel) on the crankshaft, creating irregular sensor readings
• Contamination or debris on the sensor tip affecting magnetic field detection
• Poor electrical connections at the sensor plug or ECM terminals caused by corrosion or moisture intrusion
• ECM software issues or internal ECM faults (less common but possible in older machines)

How to Troubleshoot and Fix Code P0335

Step 1: Visual Inspection Begin by inspecting the CKP sensor and its wiring harness for obvious damage. Check for rubbed-through insulation, corroded connectors, or loose mounting bolts. On used excavators, pay special attention to harness routing near the flywheel housing where engine vibration causes accelerated wear.

Step 2: Electrical Testing Using a digital multimeter, check the sensor's resistance (typically 200-900 ohms, but verify with Sumitomo specifications). Disconnect the sensor connector and measure resistance across the sensor terminals. Also test for proper voltage supply (usually 5V or 12V reference voltage) from the ECM at the harness connector.

Step 3: Sensor Gap and Reluctor Inspection Verify the air gap between the CKP sensor tip and reluctor ring meets manufacturer specifications (typically 0.5-1.5mm). Inspect the reluctor ring for missing teeth, cracks, or excessive buildup. Clean the sensor tip with electrical contact cleaner.

Step 4: Signal Testing If possible, use diagnostic software compatible with Sumitomo systems to monitor the CKP sensor signal in real-time during cranking. An erratic or missing waveform confirms sensor or reluctor issues.

Step 5: Component Replacement Replace the CKP sensor if testing reveals out-of-spec readings or visible damage. For used machines, also replace corroded connectors and repair damaged harness sections with proper heat-shrink terminals and protective sleeving.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Sumitomo service manual for your specific model and consider professional assistance for complex electrical diagnostics or ECM-related issues.