What is Hitachi ZX350LCK-5G Fault Code 13304-2?

Fault Code 13304-2 indicates a malfunction in the aftertreatment diesel oxidation catalyst (DOC) inlet temperature sensor circuit, specifically detecting an abnormal voltage signal or intermittent connection. This code is part of the Hitachi ZX350LCK-5G's emissions control system, which monitors exhaust temperatures to ensure optimal regeneration of the diesel particulate filter (DPF) and proper function of the selective catalytic reduction (SCR) system.

This fault is critical because the engine control module (ECM) relies on accurate temperature data to manage regeneration cycles and protect aftertreatment components from thermal damage. On used excavators, this sensor circuit is particularly vulnerable to heat cycling, vibration, and corrosion—all factors that accelerate wear on aging machines.

Common Symptoms

• Yellow or amber exhaust aftertreatment warning light illuminated on the instrument cluster
• Engine derate mode activated, limiting machine power to 75-80% of normal output after extended operation with active fault
• Frequent or failed DPF regeneration attempts, causing excessive fuel consumption and white smoke during regeneration cycles
• Intermittent code appearance that clears and returns, especially during temperature fluctuations or machine vibration
• Abnormal exhaust system behavior, including difficulty completing parked regeneration procedures

Potential Causes

The most common causes for Code 13304-2 on used ZX350LCK-5G excavators include:

• Corroded or damaged wiring connectors at the DOC inlet temperature sensor, especially where the harness routes near the exhaust manifold
• Failed temperature sensor due to thermal stress or internal element degradation (common after 5,000+ operating hours)
• Harness chafing or pinch points where the sensor cable contacts the frame or exhaust components during boom/arm movement
• Poor ground connections in the aftertreatment system wiring, often caused by rust or loose mounting bolts
• ECM internal fault (rare, but possible on high-hour machines with electrical system history)
• Moisture intrusion into sensor connectors from pressure washing or working in wet conditions

How to Troubleshoot and Fix Code 13304-2

Step 1: Visual Inspection Begin with a thorough inspection of the DOC inlet temperature sensor and its wiring harness. The sensor is located at the inlet of the diesel oxidation catalyst, typically on the right side of the exhaust system. Check for physical damage, melted insulation, or obvious corrosion on the connector. On used excavators, pay special attention to harness routing—look for wear marks where cables may rub against metal surfaces during machine operation.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. At room temperature (68°F/20°C), resistance should typically read between 90-110 ohms (consult your service manual for exact specifications). Next, check circuit voltage with the sensor disconnected and ignition on—you should see approximately 5 volts supply voltage from the ECM. Also verify ground continuity (less than 1 ohm resistance to chassis ground).

Step 3: Connector and Harness Verification Inspect the sensor connector for bent pins, corrosion, or moisture. Clean contacts with electrical contact cleaner and apply dielectric grease. Trace the harness back to the ECM, checking for pinch points, especially near mounting brackets or where the harness passes through the frame. On machines with over 8,000 hours, harness replacement may be more cost-effective than repeated repairs.

Step 4: Component Replacement and Verification If testing confirms sensor failure, replace with a genuine Hitachi or OEM-equivalent temperature sensor (part number specific to ZX350LCK-5G). After installation, clear codes using Hitachi Dr.EX diagnostic software or compatible scan tool. Perform a regeneration cycle and monitor live data to confirm the sensor reads within normal parameters (typically 300-750°F during operation).

Disclaimer: This guide provides general diagnostic information. Always consult the official Hitachi service manual for your specific machine serial number and consider professional diagnosis for complex electrical issues or if you're unfamiliar with high-voltage systems.