Kobelco SK140LC-8 Fault Code B173: Complete Diagnostic Guide

What is Kobelco SK140LC-8 Fault Code B173?

Fault Code B173 on the Kobelco SK140LC-8 indicates a malfunction in the air conditioner pressure sensor circuit. This code is triggered when the excavator's Electronic Control Module (ECM) detects abnormal voltage readings from the A/C pressure sensor, which monitors refrigerant pressure in the climate control system.

The air conditioner pressure sensor plays a critical role in protecting the A/C compressor from damage due to over-pressurization or low refrigerant conditions. When this sensor circuit malfunctions, the ECM cannot accurately monitor system pressure, potentially leading to compressor clutch disengagement or complete A/C system shutdown. While this code doesn't directly affect hydraulic or engine performance, it impacts operator comfort and can indicate electrical issues that may affect other systems on used machines.

Common Symptoms

When fault code B173 is active on your SK140LC-8, you may experience:

• A/C system completely non-functional despite controls being activated
• Climate control panel warning indicator illuminated on the operator display
• Compressor clutch fails to engage when A/C is turned on
• Intermittent A/C operation that cuts in and out unexpectedly
• Error message displayed on the multi-function monitor screen

Potential Causes

The most common technical reasons for B173 appearing on used Kobelco SK140LC-8 excavators include:

• Damaged or corroded wiring harness connections at the A/C pressure sensor (common wear point near the condenser)
• Failed A/C pressure sensor due to age, vibration, or refrigerant contamination
• Broken or frayed wires in the harness running from the sensor to the ECM (check routing near cab pivot points)
• Poor ground connection at the sensor mounting location or ECM ground points
• ECM internal fault (rare, but possible in high-hour used machines)
• Refrigerant system leaks causing abnormal pressure readings that appear as sensor faults

How to Troubleshoot and Fix Code B173

Step 1: Visual Inspection Begin by locating the A/C pressure sensor on the high-pressure refrigerant line near the condenser. Inspect the wiring harness for obvious damage, chafing against frame components, or corrosion at the connector. On used excavators, pay special attention to harness routing near moving parts or heat sources that may have caused insulation breakdown over time.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and check for supply voltage (typically 5V) at the harness-side connector with the ignition on. Test ground continuity between the sensor ground pin and a known good chassis ground. Measure sensor resistance according to Kobelco specifications (usually 1-5kΩ depending on ambient temperature). Compare readings against factory specifications in the service manual.

Step 3: Connector and Harness Verification Inspect connector pins for corrosion, bent terminals, or moisture intrusion—extremely common on older machines. Clean connections with electrical contact cleaner and apply dielectric grease. Perform a wiggle test while monitoring live data with Kobelco diagnostic software to identify intermittent connection faults.

Step 4: Component Replacement or Repair If electrical tests confirm sensor failure, replace the A/C pressure sensor with a genuine Kobelco or OEM-equivalent part. If wiring damage is found, repair using proper gauge wire and heat-shrink connections rather than simple butt connectors. After repairs, clear the code using diagnostic software and verify proper A/C operation under load.

Disclaimer: This guide provides general diagnostic information for Kobelco SK140LC-8 excavators. Always consult the manufacturer's service manual for exact specifications and procedures. If you're uncomfortable performing electrical diagnostics or A/C system work, contact a certified Kobelco technician or qualified heavy equipment mechanic for professional assistance.