What is Komatsu PC110-8M0 Fault Code S-6?

Fault Code S-6 on the Komatsu PC110-8M0 excavator indicates a malfunction in the engine air intake temperature sensor circuit. This diagnostic trouble code specifically points to an abnormal voltage signal being received by the Engine Control Module (ECM) from the intake air temperature (IAT) sensor, which monitors the temperature of air entering the combustion chamber.

The IAT sensor plays a critical role in the PC110-8M0's fuel injection system by providing real-time data that helps the ECM calculate the correct air-fuel mixture. When this sensor circuit fails, the engine control system cannot accurately adjust fuel delivery, potentially leading to reduced performance, increased fuel consumption, and higher emissions. For used excavators, this code often surfaces due to sensor degradation or wiring issues common in machines with significant operating hours.

Common Symptoms

When Code S-6 is active on your Komatsu PC110-8M0, you may experience:

• Check engine warning light illuminated on the instrument panel
• Reduced engine power or noticeable loss of throttle response, especially during cold starts
• Black smoke from exhaust indicating rich fuel mixture due to faulty temperature compensation
• Rough idling or hesitation during acceleration as the ECM defaults to preset values
• Increased fuel consumption as the engine management system cannot optimize combustion efficiency

Potential Causes

The most common technical reasons for Code S-6 appearing include:

• Failed IAT sensor due to internal component degradation (common in excavators with 5,000+ operating hours)
• Damaged or corroded wiring harness between the sensor and ECM, particularly at connector pins exposed to moisture and debris
• Short circuit to ground caused by wire insulation rubbing against the intake manifold or engine block
• Open circuit from broken wires inside the harness protective sheathing, especially near flex points
• Corroded electrical connectors at the sensor plug, a frequent issue on used machines stored outdoors
• ECM internal fault (rare, but possible on older control modules with water intrusion history)

How to Troubleshoot and Fix Code S-6

Step 1: Visual Inspection Begin by locating the IAT sensor on the air intake manifold (typically near the air filter housing). Disconnect the electrical connector and inspect both the sensor terminals and harness connector for corrosion, bent pins, or moisture contamination. On used excavators, carefully examine the entire wiring harness for abrasion points where it contacts metal surfaces—this is a common failure point on the PC110-8M0.

Step 2: Test Sensor Resistance Using a digital multimeter, measure the resistance across the IAT sensor terminals. At room temperature (approximately 20°C/68°F), the sensor should read between 2,000-3,000 ohms (consult your service manual for exact specifications). If the reading shows infinite resistance (open circuit) or zero ohms (short circuit), replace the sensor.

Step 3: Check Circuit Voltage and Continuity With the connector still disconnected, turn the ignition to the ON position (engine off). Measure the reference voltage at the harness connector—you should see approximately 5 volts from the ECM. Then, perform a continuity test on the signal and ground wires back to the ECM connector. Any reading indicating an open circuit or unexpected resistance suggests damaged wiring requiring repair or replacement.

Step 4: Clear Code and Monitor After repairs, use Komatsu diagnostic software (or a compatible scan tool) to clear the fault code from the ECM memory. Operate the machine through various temperature ranges and load conditions while monitoring for code recurrence. For used machinery, allow extended run time to ensure intermittent connection issues don't reappear.

Disclaimer: While this guide provides technical troubleshooting steps, complex electrical diagnostics should be performed by qualified technicians with proper training. Always consult the official Komatsu service manual for your specific serial number, and consider professional diagnosis if issues persist after basic repairs.