What is Hyundai R335LC-9T Fault Code 167-0?

Fault Code 167-0 on the Hyundai R335LC-9T excavator indicates a Transmission Oil Temperature Sensor Circuit Low Voltage condition. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormally low voltage signal from the transmission oil temperature sensor, typically reading below 0.5 volts when normal operating range should be 0.5-4.5 volts.

This code is critical for the R335LC-9T's hydraulic transmission system because the ECM relies on accurate temperature data to regulate transmission performance, prevent overheating, and optimize hydraulic oil viscosity. When this sensor circuit fails, the machine may enter derate mode to protect the transmission from potential thermal damage, significantly reducing productivity on the job site.

Common Symptoms

When Code 167-0 is active on your Hyundai R335LC-9T, operators typically experience:

• Transmission warning light illuminated on the instrument cluster (amber or red depending on severity)
• Reduced engine power or automatic derate limiting machine to 1,500-1,800 RPM
• Sluggish hydraulic response during attachment operations or swing functions
• Transmission overheat alarm even when fluid temperature feels normal to touch
• Machine may default to cold-start transmission mapping, causing harsh shifting or delayed engagement

Potential Causes

The most common technical reasons for Code 167-0 on used R335LC-9T excavators include:

• Damaged or shorted sensor wiring harness near the transmission housing where vibration and heat cause insulation breakdown
• Corroded connector pins at the transmission temperature sensor plug (common on machines operating in wet or marine environments)
• Failed transmission oil temperature sensor with internal short circuit to ground
• Chafed wiring at known rub points behind the hydraulic pump or along the mainframe rail
• ECM internal fault or poor ground connection at controller mounting point (less common but possible on high-hour machines)

How to Troubleshoot and Fix Code 167-0

Step 1: Visual Inspection and Connector Check Locate the transmission oil temperature sensor on the left side of the transmission case near the oil filter housing. Disconnect the sensor connector and inspect for:

• Corroded or bent pins
• Moisture or oil contamination inside connector
• Physical damage to connector body

Clean connector with electrical contact cleaner and apply dielectric grease before reconnecting.

Step 2: Sensor Resistance Testing Using a digital multimeter (DMM), measure resistance across the sensor terminals with connector disconnected:

• At 68°F (20°C): should read approximately 2,500-3,500 ohms
• At 176°F (80°C): should read approximately 250-350 ohms

If readings are zero ohms or infinite resistance, replace the sensor.

Step 3: Circuit Voltage and Harness Testing With ignition ON and sensor disconnected, check supply voltage at the harness connector:

• Should measure 5.0 volts ±0.25V on the signal wire
• Ground circuit should show less than 0.5 ohms to chassis ground

For used excavators, physically trace the wiring harness from sensor to ECM, checking for rubbed insulation at the transmission mounting bracket and steering cylinder routing area—common failure points on R335LC-9T models with 5,000+ operating hours.

Step 4: ECM and Software Verification If sensor and wiring test correctly, connect Hyundai Hi-MATE diagnostic software to verify ECM functionality and check for software updates. Occasionally, ECM calibration issues cause false low-voltage readings.

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Disclaimer: This guide provides general diagnostic information for Hyundai R335LC-9T excavators. Always consult the manufacturer's service manual and consider professional diagnosis for complex electrical issues. Improper repairs may void warranties or create safety hazards.