What is Case Excavator Fault Code 0108?

Fault Code 0108 on Case excavators indicates a Barometric Pressure Sensor Circuit Low Voltage condition. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects voltage readings from the barometric pressure sensor that fall below the manufacturer's specified threshold, typically under 0.5 volts.

The barometric pressure sensor measures atmospheric pressure to help the ECM calculate proper air density for fuel injection timing and quantity. On Case machines, this sensor is critical for maintaining optimal engine performance, fuel efficiency, and emissions compliance across different elevations. When voltage drops too low, the ECM cannot accurately compensate for altitude changes, leading to incorrect fuel-air mixture calculations that can compromise power output and increase fuel consumption.

Common Symptoms

• Check Engine Light (CEL) or amber warning lamp illuminated on the instrument cluster
• Noticeable loss of engine power or reduced hydraulic performance, especially at higher elevations
• Black smoke from the exhaust indicating overfueling due to incorrect pressure compensation
• Engine rough idling or hesitation during acceleration under load
• Possible engine derating or limp mode activation on newer Case models with emissions controls

Potential Causes

The most frequent causes of Code 0108 on used Case excavators include:

• Damaged wiring harness or connector pins at the sensor, particularly from chafing against frame members near the intake manifold
• Corroded or loose connector terminals due to moisture intrusion (common on machines stored outdoors)
• Failed barometric pressure sensor internal circuit, especially on excavators with 5,000+ operating hours
• Shorted sensor ground wire creating a path to chassis ground before reaching the ECM
• Faulty ECM (rare, but possible on heavily used machines with electrical system history)

How to Troubleshoot and Fix Code 0108

Step 1: Visual Inspection Locate the barometric pressure sensor (typically mounted on the intake manifold or ECM housing). Inspect the wiring harness for obvious damage, wear marks, or pinch points. Check the connector for corrosion, bent pins, or moisture—critical on used equipment.

Step 2: Electrical Testing Using a digital multimeter, backprobe the sensor connector with the ignition ON/engine OFF. Verify supply voltage is present (should be approximately 5 volts from the ECM). Check ground circuit continuity to ensure less than 0.5 ohms resistance to chassis ground.

Step 3: Sensor Signal Testing Measure the signal voltage from the sensor (typically 3.5-4.5 volts at sea level). If voltage reads below 0.5 volts, disconnect the sensor and test resistance across sensor terminals—should be within manufacturer specifications (usually 20-80 ohms depending on model).

Step 4: Component Replacement If sensor tests faulty, replace with OEM or equivalent part. On used excavators, always apply dielectric grease to connector terminals before reassembly to prevent future corrosion. Clear codes using Case diagnostic software (CNH EST) or compatible scan tool, then perform a test run at varying loads.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Case service manual for your specific model and serial number. If unfamiliar with electrical diagnostics, consult a certified heavy equipment technician to prevent further damage.