What is Kobelco SK200-8 Fault Code B173?

Kobelco SK200-8 Fault Code B173 indicates a malfunction in the Auto Air Conditioner Interior Temperature Sensor circuit. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormal voltage signal or open/short circuit condition from the cabin interior temperature sensor within the automatic climate control system.

While not directly affecting the excavator's hydraulic or propulsion systems, this fault compromises operator comfort and productivity, especially in extreme climates. The interior temperature sensor continuously monitors cabin air temperature to maintain the operator's set climate preferences. When the ECM cannot receive accurate temperature data, the automatic A/C system defaults to manual operation or fails to regulate properly, reducing operator efficiency during long shifts on used excavators where environmental control becomes critical for performance.

Common Symptoms

• A/C warning light illuminated on the climate control panel or monitor display
• Automatic climate control system fails to adjust temperature despite changing cabin conditions
• Air conditioning system blows at constant speed regardless of temperature settings
• No response when adjusting automatic temperature controls; system remains in manual mode only
• Intermittent A/C operation, particularly noticeable when equipment operates on uneven terrain causing connector vibration

Potential Causes

The most common technical causes for Code B173 on used SK200-8 excavators include:

• Interior temperature sensor failure due to age-related component degradation or contamination from dust ingress
• Damaged or corroded wiring harness connections between the sensor and climate control ECU, particularly at connector points behind the dashboard
• Open or short circuit in the sensor signal wire, often caused by harness chafing against metal cab structures during long-term operation
• Poor ground connection at the sensor mounting location or ECU ground points
• ECU internal fault (less common), typically seen in machines with water intrusion history into the electrical cab

How to Troubleshoot and Fix Code B173

Step 1: Visual Inspection Begin by accessing the climate control panel and locating the interior temperature sensor (typically mounted near the A/C air intake vent inside the cab). Inspect the wiring harness for visible damage, worn insulation, or connector corrosion. On used excavators, check for evidence of previous repairs or modified wiring that may create intermittent connections.

Step 2: Electrical Testing Using a digital multimeter, disconnect the interior temperature sensor connector and measure resistance across the sensor terminals. Compare readings against Kobelco specifications (typically 2-3 kΩ at 20°C ambient temperature). Check for continuity between the sensor signal wire and ECU connector. Measure supply voltage at the sensor connector (should read approximately 5V DC with ignition on).

Step 3: Connector and Ground Verification Clean all connector pins with electrical contact cleaner and inspect for bent terminals or moisture intrusion—common issues in used machines. Verify ground circuit continuity between the sensor ground and chassis ground. Test harness for shorts to power or ground using the multimeter's continuity function.

Step 4: Component Replacement If sensor resistance is out of specification or wiring tests reveal circuit faults, replace the defective component. For used excavators, always inspect connector seals and apply dielectric grease during reassembly to prevent future corrosion. Clear fault codes using Kobelco diagnostic software and verify system operation under various temperature conditions.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Kobelco service manual for your specific machine serial number and consider professional diagnostic assistance for complex electrical issues.