What is Hyundai R805LC-7 Fault Code 167-0?

Fault Code 167-0 on the Hyundai R805LC-7 excavator indicates a Transmission Oil Temperature Sensor Circuit malfunction, specifically reporting an abnormal voltage reading or open circuit condition. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects voltage readings outside the normal operational range (typically 0.5-4.5V) from the transmission oil temperature sensor circuit.

The transmission oil temperature sensor plays a critical role in the R805LC-7's hydraulic system performance. It monitors the hydraulic oil temperature and sends real-time data to the ECM, which adjusts pump flow, engine RPM limits, and activates warning systems to prevent overheating damage. On this particular model, the sensor is located on the transmission oil cooler circuit, an area known for exposure to debris and vibration-related failures in used machines.

Common Symptoms

When Code 167-0 is active, operators typically experience:

• Transmission overheat warning light illuminated on the instrument cluster, often accompanied by an audible alarm
• Automatic engine derate or reduced power mode, limiting machine productivity to protect hydraulic components
• Inaccurate or frozen temperature gauge readings on the monitor display
• Intermittent fault code appearance, especially during cold starts or after extended operation
• In severe cases, the machine may enter limp mode, restricting hydraulic functions and travel speed

Potential Causes

The most common technical reasons for Code 167-0 on used R805LC-7 excavators include:

• Faulty transmission oil temperature sensor due to internal resistance drift or element failure (common after 8,000+ operating hours)
• Damaged or corroded wiring harness at known rub points near the hydraulic oil cooler mounting bracket
• Loose or oxidized electrical connectors, particularly the 2-pin Deutsch connector at the sensor junction
• ECM internal fault or corrupted calibration data (rare, but documented in earlier production units)
• Broken sensor mounting boss causing the sensor to lose proper contact with hydraulic fluid
• Previous repairs using incorrect aftermarket sensors with incompatible resistance curves

How to Troubleshoot and Fix Code 167-0

Step 1: Visual Inspection and Data Retrieval Connect Hyundai Hi-MATE diagnostic software or compatible scan tool to retrieve active and pending codes. Record freeze frame data showing temperature values when the fault occurred. Physically inspect the sensor location on the transmission oil cooler for obvious damage, oil leaks, or loose mounting.

Step 2: Electrical Circuit Testing Disconnect the sensor's 2-pin connector and inspect for bent pins, corrosion (green oxidation), or moisture intrusion. Using a digital multimeter (DMM), measure sensor resistance at room temperature (should read approximately 2,200-2,800 ohms at 20°C). Then check wiring harness continuity from the sensor connector to ECM pins (refer to service manual for specific pin locations). Look for resistance above 5 ohms indicating corrosion or damaged wires.

Step 3: Voltage Supply Verification With the ignition on and sensor disconnected, measure voltage at the harness connector. You should see approximately 5V reference voltage from the ECM on one pin and a proper ground (below 0.1V) on the other. Deviations indicate ECM supply issues or harness shorts to ground/power.

Step 4: Sensor Replacement and Used Equipment Considerations For used excavators, thoroughly inspect the harness routing along the cooler frame where vibration causes insulation wear. Replace the sensor with a genuine Hyundai part (P/N 31E9-02870 or equivalent), as aftermarket sensors often have incorrect resistance tables causing false codes. After installation, clear codes, operate the machine through temperature cycles, and verify the code doesn't return.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Hyundai R805LC-7 service manual and consider professional diagnostic assistance for complex electrical issues or if unfamiliar with high-voltage systems.