## What is Kobelco SK460-8 Fault Code B173?

**Fault Code B173 on the Kobelco SK460-8 excavator indicates a malfunction in the pilot pressure sensor circuit.** This diagnostic trouble code (DTC) is triggered when the **Engine Control Module (ECM)** detects an abnormal voltage signal from the pilot pressure sensor, which monitors the hydraulic pilot pressure used to control the machine's attachments and functions.

The pilot pressure sensor is critical for the SK460-8's performance because it communicates real-time hydraulic pressure data to the ECM. This information allows the machine to optimize engine speed, hydraulic flow, and fuel consumption based on operator input. When Code B173 appears, the excavator may enter a **derate mode** or experience compromised hydraulic response, directly impacting productivity and operational safety.

## Common Symptoms

When fault code B173 is active on your Kobelco SK460-8, operators typically experience:

- **Illuminated warning light** on the instrument panel, often accompanied by an audible alarm
- **Reduced hydraulic response** or sluggish attachment movements during operation
- **Engine derate mode**, limiting maximum RPM and reducing overall machine power
- **Erratic bucket or arm control**, particularly during fine positioning work
- **Intermittent loss of hydraulic functions** when the sensor signal fluctuates

## Potential Causes

The most common technical reasons for Code B173 appearing on used SK460-8 excavators include:

- **Faulty pilot pressure sensor** due to internal component failure or contamination from hydraulic fluid
- **Damaged wiring harness** between the sensor and ECM, particularly at known rub points near the hydraulic pump
- **Corroded or loose electrical connectors** at the sensor or ECM terminals (common in machines with high operating hours)
- **Short circuit to ground** caused by wire insulation breakdown from heat exposure or mechanical abrasion
- **ECM internal fault** affecting the sensor's 5-volt reference circuit or signal processing capability
- **Contaminated hydraulic oil** causing sensor membrane degradation in older machines

## How to Troubleshoot and Fix Code B173

**Step 1: Visual Inspection and Connector Check**

Begin by locating the **pilot pressure sensor** on the hydraulic pilot circuit (typically mounted on or near the main control valve). Inspect the sensor's electrical connector for corrosion, moisture, or damaged pins. On used excavators, this is a critical first check as environmental exposure commonly compromises these connections. Clean connectors with **electrical contact cleaner** and ensure tight, secure connections.

**Step 2: Voltage and Resistance Testing**

Using a **digital multimeter (DMM)**, check the sensor's power supply. With the ignition on and sensor disconnected, verify **5-volt reference voltage** at the harness connector. Then measure the sensor's internal resistance (typically 100-300 ohms, but consult the Kobelco service manual for exact specifications). Compare readings against factory specifications to determine if sensor replacement is necessary.

**Step 3: Wiring Harness Continuity Check**

Trace the **wiring harness** from the sensor to the ECM, paying special attention to areas where cables route near moving components or sharp edges. Check for continuity between each wire using your multimeter, and measure resistance to ground on the signal wire (should be infinite/open). For used machines, inspect common wear points near the swing bearing and hydraulic pump mounting areas where harness chafing frequently occurs.

**Step 4: Sensor Replacement and System Verification**

If testing confirms a faulty sensor, replace it with a **genuine Kobelco pilot pressure sensor** to ensure proper calibration. After installation, clear the fault code using **Kobelco diagnostic software** (KOBCONNECT) or a compatible scan tool. Cycle the ignition, operate the hydraulics through full range of motion, and verify the code does not return. Monitor hydraulic pressure readings in the diagnostic software to confirm proper sensor operation.

**Step 5: Advanced Diagnostics**

If the code persists after sensor and harness verification, the issue may lie within the **ECM itself**. This requires specialized diagnostic equipment and expertise. Before replacing the ECM (a costly repair on used equipment), verify all ground connections are clean and tight, and check for software updates available through Kobelco dealers.

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**Disclaimer:** This guide provides general troubleshooting information for Kobelco SK460-8 fault code B173. Always consult the manufacturer's service manual and consider professional diagnostic assistance, especially when working with electrical systems. Improper repairs may cause additional damage or safety hazards.