What is Volvo Excavator Fault Code SID70 FMI2 (128SID70HE2501)?

Fault Code SID70 FMI2 indicates an erratic or intermittent signal from the Engine Oil Pressure (EOP) sensor on Volvo excavators. This diagnostic trouble code (DTC) is generated when the Electronic Control Module (ECM) detects voltage fluctuations or inconsistent readings from the oil pressure sensor circuit that fall outside normal operating parameters.

The SID (Subsystem Identifier) 70 specifically refers to the engine oil pressure sensor, while FMI (Failure Mode Identifier) 2 designates an erratic or intermittent electrical signal. This fault is critical because the ECM relies on accurate oil pressure data to protect the engine from catastrophic damage due to inadequate lubrication. On Volvo machines, this code can trigger protective measures that limit engine performance or initiate shutdown protocols to prevent internal engine damage.

Common Symptoms

• Intermittent amber or red warning lights on the instrument cluster, specifically the oil pressure warning lamp
• Engine derate or power reduction mode activated as a protective measure, limiting machine productivity
• Erratic oil pressure gauge readings that fluctuate abnormally or show inconsistent values during operation
• Engine shutdown or failure to start in severe cases when the ECM cannot verify adequate oil pressure
• Diagnostic fault messages displayed on the multi-function display indicating oil pressure system faults

Potential Causes

The most common technical reasons for Code SID70 FMI2 on used Volvo excavators include:

• Corroded or loose electrical connectors at the oil pressure sensor, particularly common in high-vibration environments or machines with extended service hours
• Damaged wiring harness with chafing or rubbing against engine components, especially near the sensor mounting location on the engine block
• Failing oil pressure sensor with internal electrical degradation causing intermittent signal output
• Poor ground connections in the sensor circuit due to corrosion or loose mounting bolts
• ECM connector issues including corroded pins or moisture intrusion in the engine control module connections
• Low engine oil level or contaminated oil causing actual pressure fluctuations that appear as erratic sensor readings

How to Troubleshoot and Fix Code SID70 FMI2

Step 1: Visual Inspection and Connection Check Begin by locating the engine oil pressure sensor (typically mounted on the engine block near the oil filter). Disconnect the sensor connector and carefully inspect both the sensor pins and harness connector for corrosion, bent pins, or oil contamination. Clean connections with electrical contact cleaner and apply dielectric grease before reconnecting. For used excavators, pay special attention to harness routing—look for wear points where the wiring may rub against the engine or frame.

Step 2: Electrical Testing with Diagnostic Tools Using a digital multimeter (DMM), perform resistance and voltage checks on the sensor circuit. With the key on and engine off, backprobe the sensor connector to measure supply voltage (typically 5 volts from the ECM). Check circuit resistance with the sensor disconnected; readings should match Volvo specifications (generally 50-250 ohms depending on temperature). Use Volvo VCADS (Volvo Construction Equipment Advanced Diagnostic System) or compatible diagnostic software to monitor live sensor data and observe for signal dropouts or erratic voltage patterns.

Step 3: Component Replacement and Verification If electrical testing reveals intermittent signals despite good connections, replace the oil pressure sensor with a genuine Volvo part or high-quality OEM equivalent. Before installation, verify actual engine oil pressure using a mechanical oil pressure gauge to rule out genuine low-pressure conditions. After sensor replacement, clear fault codes using diagnostic software and perform an extended test run while monitoring sensor output. For used machines with high hours, inspect the engine wiring harness for hidden damage and consider replacing corroded or brittle sections.

Disclaimer: This guide provides general diagnostic information. Always consult the official Volvo service manual for your specific machine model and serial number. If you're uncomfortable performing electrical diagnostics or if the fault persists after basic troubleshooting, contact a certified Volvo technician or authorized service center for professional assistance.