What is Volvo Excavator Fault Code 128PID110SE2606-2?

Fault Code 128PID110SE2606-2 indicates an Engine Coolant Temperature (ECT) sensor circuit voltage is above normal or shorted high (Data Valid But Above Normal Operating Range). This code specifically relates to PID 110 (Engine Coolant Temperature) with a SPN 110/FMI 2 designation in J1939 diagnostic protocols used by Volvo construction equipment.

This fault means the Engine Control Module (ECM) is receiving an abnormally high voltage signal from the coolant temperature sensor, typically above 4.5 volts when normal operating range should be 0.5-4.5 volts. For Volvo excavators, accurate coolant temperature monitoring is critical for preventing engine overheating, managing fan speed operation, controlling fuel injection timing, and triggering appropriate derate modes to protect the diesel engine from catastrophic damage.

Common Symptoms

When this fault code is active, operators typically experience:

• Check Engine Light or Engine Warning Lamp illuminated on the instrument cluster
• Engine derate or power reduction mode activated, limiting machine performance to prevent perceived overheating
• Cooling fan running continuously at high speed, even when engine is cold
• Difficulty starting or rough idle due to incorrect fuel mapping based on faulty temperature data
• Inaccurate temperature gauge readings showing abnormally low or no temperature reading on display

Potential Causes

The most common technical causes for this fault code in used Volvo excavators include:

• Open circuit in coolant temperature sensor wiring harness due to wire breakage, particularly at flex points near the engine block
• Damaged or corroded connector pins at the ECT sensor or ECM connection points (common in machines exposed to harsh environments)
• Failed coolant temperature sensor with internal open circuit condition
• Chafed or rubbed-through wiring along the main engine harness routing, especially where harness contacts frame rails or sharp edges
• Poor ground connection at the sensor or ECM ground points due to corrosion buildup
• ECM internal fault (less common, but possible in high-hour machines)

How to Troubleshoot and Fix Code 128PID110SE2606-2

Step 1: Visual Inspection Begin with a thorough physical inspection of the coolant temperature sensor located on the engine block (typically near the thermostat housing). Check for damaged connectors, corroded pins, or coolant contamination on the electrical connector. On used excavators, pay special attention to harness wear points where the wire bundle flexes or contacts metal surfaces.

Step 2: Electrical Testing at Sensor Disconnect the ECT sensor connector and use a digital multimeter to measure resistance across the sensor terminals. A functioning sensor should read approximately 2,000-3,000 ohms at room temperature (68°F/20°C), decreasing as temperature increases. An open circuit (infinite resistance) confirms sensor failure. Also check for supply voltage from the ECM at the harness connector—should read approximately 5 volts with key on, engine off.

Step 3: Harness and Circuit Testing Using Volvo VCADS (Volvo Computer Aided Diagnostic System) or compatible diagnostic software, monitor live sensor voltage while gently wiggling the harness. Voltage spikes or intermittent open circuits indicate wiring damage. Check continuity from sensor connector to ECM pins and verify ground circuit integrity (should be less than 1 ohm resistance to chassis ground).

Step 4: Component Replacement and Verification If sensor and wiring test normally, replace the coolant temperature sensor with genuine Volvo or OEM-equivalent parts. For used machines with high hours, consider replacing both the sensor and the connector pigtail to eliminate corrosion issues. After replacement, clear codes using diagnostic software, run engine through warm-up cycle, and verify code does not return.

Disclaimer: This guide provides general troubleshooting information for experienced diesel mechanics. Always consult official Volvo service documentation and consider professional diagnostic assistance for complex electrical issues or if you're unsure about any procedure.