Sumitomo SH220LC-6 Fault Code 1655: Complete Diagnostic Guide

What is Sumitomo SH220LC-6 Fault Code 1655?

Fault Code 1655 on the Sumitomo SH220LC-6 indicates a malfunction in the engine oil pressure sensor circuit or abnormally low oil pressure detection. This code is triggered when the Engine Control Module (ECM) receives a signal outside the normal operating range from the oil pressure sensor, or when actual oil pressure falls below the manufacturer's specified threshold during operation.

This fault is critical for the SH220LC-6 because inadequate oil pressure monitoring can lead to catastrophic engine damage. The Isuzu 6WG1X engine powering this excavator relies on precise oil pressure feedback to protect internal components. When this code activates, the ECM may initiate protective measures including power derate or complete shutdown to prevent bearing failure, crankshaft damage, or turbocharger seizure.

Common Symptoms

When fault code 1655 is active on your SH220LC-6, operators typically experience:

• Engine warning light illuminated on the instrument cluster, often accompanied by an audible alarm
• Power reduction or derate mode engaging, limiting maximum RPM and hydraulic performance
• Erratic oil pressure gauge readings or gauge staying at zero despite engine running
• Engine auto-shutdown in severe cases, particularly under load or at operating temperature
• Intermittent code appearance that clears and returns, especially during cold starts or high-demand operations

Potential Causes

For used SH220LC-6 excavators, fault code 1655 typically stems from these issues:

• Failed oil pressure sensor – Common wear item on machines with 5,000+ hours; sensor diaphragm deterioration
• Damaged sensor wiring harness – Vibration-induced wire chafing near the engine mount points or along the valve cover
• Corroded or loose electrical connectors – Moisture intrusion at the sensor connector, particularly on machines stored outdoors
• Low actual engine oil pressure – Worn oil pump, clogged oil filter, or excessive bearing clearances in high-hour engines
• ECM calibration issues – Rare but possible after ECM replacement or software updates
• Contaminated engine oil – Fuel dilution or coolant contamination affecting oil viscosity

How to Troubleshoot and Fix Code 1655

Step 1: Visual Inspection Begin by locating the oil pressure sensor on the right side of the engine block near the oil filter housing. Inspect the wiring harness for obvious damage, abrasion points where it contacts the engine, or oil contamination on connectors. On used excavators, check for previous repair attempts like electrical tape or spliced wires that indicate recurring issues.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to check sensor resistance. The oil pressure sensor should typically read 50-150 ohms at room temperature (consult your service manual for exact specifications). Check for continuity to ground in the wiring harness – there should be no continuity. Measure supply voltage at the harness connector with ignition on; you should see approximately 5 volts from the ECM.

Step 3: Mechanical Verification If electrical tests pass, install a mechanical oil pressure gauge in the sensor port to verify actual engine oil pressure. At operating temperature and idle, pressure should be 15-25 PSI minimum, rising to 40-60 PSI at high idle. Low readings indicate internal engine wear or oil pump problems requiring mechanical repair.

Step 4: Component Replacement Replace the oil pressure sensor with a genuine Sumitomo/Isuzu part if testing confirms sensor failure. For used machines, also replace the sensor O-ring and apply dielectric grease to the electrical connector to prevent future corrosion. Clear the fault code using diagnostic software (PC-based or handheld scanner compatible with Sumitomo systems) and perform a test run under load.

Disclaimer: This guide provides general diagnostic information. Always consult the official Sumitomo service manual for your specific machine serial number. If you're uncomfortable performing these diagnostics, or if mechanical engine issues are suspected, consult a certified heavy equipment technician to prevent further damage.