What is Case Excavator Fault Code E0373?

Fault Code E0373 indicates a malfunction in the hydraulic oil temperature sensor circuit or an out-of-range hydraulic oil temperature reading. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects abnormal voltage signals from the hydraulic oil temperature sensor, typically indicating an open circuit, short circuit, or implausible temperature value outside the programmed parameters.

This code is critical for Case excavators because the hydraulic system is the lifeblood of machine operation. The ECM relies on accurate temperature data to protect components from overheating, optimize hydraulic pump performance, and prevent catastrophic system failure. When E0373 activates, the ECM may default to a protection mode, limiting machine functionality until the issue is resolved.

Common Symptoms

When Code E0373 is active, operators typically experience:

• Warning light or fault indicator illuminated on the instrument cluster
• Reduced hydraulic performance or sluggish implement response due to ECM derate mode
• Inaccurate or blank hydraulic temperature gauge readings on the display
• Machine entering limp mode, restricting travel speed or hydraulic functions
• Intermittent code activation during cold starts or after prolonged operation

Potential Causes

The most common technical causes for E0373 on used Case excavators include:

• Faulty hydraulic oil temperature sensor due to internal resistance drift or complete failure
• Damaged or corroded wiring harness at the sensor connector, especially near frame pivot points or routing areas exposed to hydraulic fluid contamination
• Chafed or pinched sensor wires from rubbing against hydraulic lines or structural components—a known issue in high-hour machines
• Corroded or loose connector pins at the sensor or ECM connection points from moisture intrusion
• ECM software glitch or corrupted calibration data (less common but possible in older units)
• Hydraulic oil contamination causing sensor element fouling or coating

How to Troubleshoot and Fix Code E0373

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor (typically mounted on the hydraulic tank or main valve block). Inspect the sensor connector and wiring harness for obvious damage, corrosion, oil saturation, or loose connections. On used excavators, pay special attention to harness routing near articulation points where friction wear commonly occurs.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance at various temperatures (refer to Case service manual specifications—typically 2,000-3,000 ohms at room temperature). Check for voltage supply at the harness connector (usually 5V reference voltage from the ECM). Verify ground continuity and inspect for shorts to power or ground.

Step 3: Sensor Replacement and Harness Repair If resistance values are out of specification or the sensor shows physical damage, replace it with a genuine Case OEM sensor. If wiring is compromised, repair or replace the affected harness section, ensuring proper routing away from heat sources and moving components. Clear the code using Case diagnostic software (Service Advisor or compatible scan tool) and monitor for recurrence.

Critical for Used Machines: Before replacing parts, thoroughly clean all electrical connectors with contact cleaner and apply dielectric grease to prevent future corrosion—a cost-effective fix for many sensor circuit codes on older equipment.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Case service manual for your specific model and seek assistance from a qualified heavy equipment technician for complex repairs or safety-critical systems.