What is Sumitomo SH350HD-6 Fault Code 601?

Fault Code 601 on the Sumitomo SH350HD-6 excavator indicates a malfunction in the Engine Control Module (ECM) communication circuit or a critical sensor voltage abnormality within the engine management system. This code typically signals that the ECM is not receiving proper voltage signals from one or more critical sensors, or there's an interruption in the Controller Area Network (CAN) bus communication between the engine controller and the machine's main control system.

This fault is particularly critical for the SH350HD-6 because it directly affects the excavator's ability to regulate fuel injection timing, turbocharger boost pressure, and exhaust gas recirculation (EGR) functions. When this code activates, the machine may enter a protective derate mode to prevent potential engine damage, significantly impacting jobsite productivity.

Common Symptoms

• Yellow or amber warning lamp illuminated on the instrument cluster with reduced engine power output
• Engine derate mode activated, limiting maximum RPM to approximately 1,500-1,800 RPM
• Intermittent engine stalling or rough idle, especially during cold starts or when hydraulic loads are applied
• Hydraulic system sluggishness due to insufficient engine power reaching operating temperature
• Error messages displayed on the multi-function monitor indicating ECM communication failure

Potential Causes

The most common causes of Code 601 on used SH350HD-6 excavators include:

• Corroded or damaged ECM harness connectors, particularly at the main engine wiring junction near the battery box where moisture accumulation is common
• Worn or frayed CAN bus wiring behind the left-side access panel, a known rub point on machines with 5,000+ operating hours
• Failed crankshaft position sensor or camshaft position sensor sending erratic voltage signals to the ECM
• Low battery voltage or weak alternator output causing voltage drops below the 10.5V threshold required for proper ECM operation
• ECM internal failure due to moisture intrusion, particularly on machines operated in humid or marine environments

How to Troubleshoot and Fix Code 601

Step 1: Perform Visual Inspection Begin by checking all ECM harness connectors for corrosion, bent pins, or moisture. Inspect the CAN bus wiring (typically yellow and green twisted pair) behind the left operator station panel for chafing or breaks. On used excavators, this harness often rubs against the steel frame.

Step 2: Test Electrical System Voltage Using a digital multimeter, verify battery voltage exceeds 12.5V with the engine off and 13.8-14.4V with the engine running. Check for voltage drops at the ECM power supply connector (Pin 1 and Pin 15 on the 24-pin connector). Resistance between ground and chassis should be less than 0.5 ohms.

Step 3: Scan with Diagnostic Software Connect Sumitomo-compatible diagnostic software (or universal heavy equipment scan tools) to retrieve active and pending codes. Check sensor live data for the crankshaft and camshaft position sensors—voltage should fluctuate between 0.5V and 4.5V during cranking.

Step 4: Inspect Critical Sensors Remove and inspect the crankshaft position sensor located on the lower left side of the engine block. Check connector pins for corrosion and measure sensor resistance (typically 200-300 ohms). Replace if readings are out of specification.

Step 5: Address Harness Issues For used machines, carefully inspect the entire engine harness for previous repairs, electrical tape patches, or aftermarket splices. Replace any compromised sections rather than attempting further repairs, as intermittent connections will cause recurring codes.

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Disclaimer: This guide provides general troubleshooting information for Fault Code 601. Always consult the official Sumitomo service manual for your specific machine serial number and consider professional diagnostic assistance for complex electrical issues. Improper repairs may void warranties or cause additional damage.