What is Caterpillar Fault Code EID573?

Caterpillar fault code EID573 indicates an "Engine Oil Pressure Sensor Circuit - Voltage Above Normal or Shorted High." This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormally high voltage signal from the engine oil pressure sensor circuit, typically exceeding 4.5-5.0 volts when normal operating range is 0.5-4.5 volts.

This fault is critical for Caterpillar excavators because the ECM relies on accurate oil pressure data to protect the engine from catastrophic damage. When EID573 activates, the system cannot verify whether adequate lubrication is reaching critical engine components like bearings, camshafts, and turbocharger assemblies. On used machines, this code often appears due to sensor degradation or wiring harness damage from years of vibration and environmental exposure.

Common Symptoms

• Amber warning light illuminated on the instrument cluster with possible oil pressure icon
• Engine derate mode activated, limiting machine to reduced RPM (typically 1500-1800 RPM) to prevent potential damage
• Erratic or maxed-out oil pressure gauge reading showing 100+ PSI regardless of actual pressure
• Intermittent activation during cold starts or when operating on steep slopes, especially on high-hour machines
• Check Engine light with stored fault code retrievable via Cat Electronic Technician (ET) software

Potential Causes

The most common technical causes for EID573 on used Caterpillar excavators include:

• Failed oil pressure sensor with internal short circuit (common failure point after 5,000+ operating hours)
• Damaged sensor wiring harness caused by rubbing against engine block, frame rails, or hydraulic lines
• Corroded or moisture-contaminated electrical connectors at the sensor or ECM interface, particularly on machines stored outdoors
• Shorted signal wire to 5-volt reference or battery voltage within the harness bundle
• ECM internal fault (rare but possible on older control modules with 10,000+ hours)
• Aftermarket sensor incompatibility if previous repairs used non-OEM parts with incorrect resistance values

How to Troubleshoot and Fix Code EID573

Step 1: Visual Inspection of Sensor and Wiring Begin by locating the engine oil pressure sensor (typically mounted on the main oil gallery near the oil filter housing). Inspect the sensor body for oil leaks, cracks, or physical damage. Trace the sensor harness back to the ECM, checking for wire chafing, pinched insulation, or connector corrosion—common issues on used equipment operating in harsh conditions.

Step 2: Electrical Testing with Multimeter Disconnect the sensor connector and measure resistance across the sensor terminals. Compare readings against Caterpillar specifications (typically 50-250 ohms depending on model). Next, check for short to voltage by measuring from the signal wire (with sensor disconnected) to ground—any reading above 0.2 volts indicates a wiring fault. Use a digital multimeter set to voltage mode to verify the ECM is supplying correct 5-volt reference voltage at the connector.

Step 3: Component Replacement and Verification If wiring tests pass, replace the oil pressure sensor with a genuine Caterpillar part—aftermarket sensors frequently cause repeat failures on used machines. Clean all connector pins with electrical contact cleaner and apply dielectric grease to prevent future corrosion. Clear the fault code using Cat ET diagnostic software and perform an operational test under load. For persistent codes after replacement, suspect ECM failure requiring dealer-level diagnostics.

Critical Note for Used Excavators: Always inspect wire routing near high-vibration areas like engine mounts and hydraulic pumps. Securing loose harnesses with proper clamps prevents future rubbing damage common in high-hour machines.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Caterpillar service manual for your specific model and serial number. For complex electrical issues or ECM programming, seek assistance from a certified Cat dealer or qualified heavy equipment technician.