What is Kobelco SK135SRLC-2 Fault Code P0272 (663-8)?

Fault Code P0272 (663-8) indicates a malfunction in the Cylinder #4 Injector Circuit, specifically detecting low voltage or an open circuit condition in the fuel injector control system. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects abnormal electrical resistance or insufficient current flow to the number 4 cylinder's fuel injector solenoid during operation.

For the Kobelco SK135SRLC-2's diesel engine, this code is critical because proper injector circuit function directly affects fuel delivery precision, combustion efficiency, and overall engine performance. When cylinder #4 cannot receive proper fueling commands, the engine experiences power loss, increased emissions, and potential long-term damage to the affected cylinder.

Common Symptoms

When fault code P0272 is active on your SK135SRLC-2, operators typically experience:

• Engine misfiring or rough running, particularly noticeable at idle or under load
• Reduced hydraulic performance due to decreased engine power output and potential engine derate mode activation
• Increased black or white exhaust smoke from incomplete combustion in cylinder #4
• Illuminated malfunction indicator lamp (MIL) on the instrument cluster with reduced power warning
• Difficulty starting or extended cranking time, especially in cold weather conditions

Potential Causes

The most common technical failures triggering P0272 on used Kobelco excavators include:

• Damaged or corroded wiring harness at injector connector—a frequent issue on older machines due to engine vibration and heat cycling
• Failed fuel injector solenoid in cylinder #4 from internal coil breakdown or mechanical wear
• Frayed wiring or harness rub-through along the valve cover routing path where the harness contacts engine components
• Corroded connector pins at the injector plug caused by moisture intrusion or oil contamination
• ECM internal driver circuit failure affecting only the #4 injector output channel
• Poor ground connections at engine block ground points due to rust or loose fasteners

How to Troubleshoot and Fix Code P0272 (663-8)

Step 1: Visual Inspection Begin by thoroughly inspecting the injector wiring harness from the ECM to cylinder #4. On used SK135SRLC-2 models, check for harness wear where it passes near the exhaust manifold and valve cover. Look for melted insulation, exposed copper, or oil-soaked connectors indicating seal failures.

Step 2: Electrical Testing Using a digital multimeter, disconnect the #4 injector connector and measure resistance across the injector solenoid terminals. Typical specification is 0.3-0.8 ohms; readings outside this range indicate injector failure. Next, check for voltage supply at the harness connector with ignition on—you should see battery voltage (12-14V).

Step 3: Connector and Ground Verification Inspect the injector connector for corrosion, bent pins, or moisture. Clean with electrical contact cleaner and apply dielectric grease. Verify engine ground integrity by measuring resistance between ECM ground and battery negative—resistance should be less than 1 ohm.

Step 4: Diagnostic Software Confirmation If available, use Kobelco diagnostic software or compatible scan tool to perform an injector cutout test, which isolates each cylinder to confirm #4 is the affected injector. This eliminates guesswork before parts replacement.

Step 5: Component Replacement For used excavators with high hours, if testing confirms injector failure, replace the fuel injector assembly with OEM or quality aftermarket parts. Always replace the injector O-rings and copper washers simultaneously to prevent fuel leaks and future codes.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Kobelco service manual for your specific machine serial number and consider professional diagnostic support for complex electrical issues or if you lack proper testing equipment.