Hyundai HX220 NL EPFC Fault Code 167-4: Complete Diagnostic Guide

What is Hyundai HX220 NL EPFC Fault Code 167-4?

Fault Code 167-4 indicates a voltage issue with the Intake Air Heater Circuit on the Hyundai HX220 NL EPFC excavator, specifically signaling that the voltage has fallen below the normal operating range. This code is triggered when the Electronic Control Module (ECM) detects insufficient voltage supply to the intake air heater system, which is critical for cold-weather starting and efficient combustion.

The intake air heater (also called a grid heater or intake manifold heater) preheats incoming air before it enters the combustion chamber. On diesel engines like those in the HX220 NL, this component is essential for reliable cold starts and optimal fuel atomization. When voltage drops below threshold values—typically under 10.5 volts during heater activation—the ECM logs this fault to prevent component damage and alert operators to potential electrical system problems.

Common Symptoms

When Code 167-4 is active, operators typically experience:

• Difficult cold starts or extended cranking time, especially in temperatures below 40°F (4°C)
• White or gray exhaust smoke during initial startup due to incomplete combustion
• Check engine light or warning indicator illuminated on the instrument cluster
• Reduced engine performance during the warm-up phase with possible rough idling
• Intermittent code activation that may clear after the engine reaches operating temperature

Potential Causes

The most common technical reasons for Code 167-4 on used HX220 NL excavators include:

• Corroded or loose battery terminals reducing overall system voltage during high-draw startup
• Failing intake air heater element with increased resistance or internal short circuits
• Damaged wiring harness between the ECM and heater relay, particularly at flex points near the engine mount
• Defective heater relay stuck open or with degraded contacts causing voltage drop
• Weak or aging batteries unable to maintain voltage under load (common in machines with 3,000+ hours)
• Poor ground connections at the engine block or chassis ground points
• ECM power supply issues including corroded connectors at the main engine harness

How to Troubleshoot and Fix Code 167-4

Step 1: Perform Initial Voltage Testing Using a digital multimeter, check battery voltage with the engine off (should read 12.4-12.8V) and during cranking (should not drop below 10V). Test voltage at the intake air heater connector during activation—it should match battery voltage within 0.5V.

Step 2: Inspect Electrical Connections On used excavators, examine all wiring harness connections from the battery to the intake heater relay and from the relay to the heater element. Look for corrosion, frayed wires, or rubbing damage at common wear points near the engine mounts and along the frame rail. Clean all ground connections with a wire brush and apply dielectric grease.

Step 3: Test the Intake Air Heater and Relay Disconnect the heater and measure resistance across its terminals (typically 0.5-2.0 ohms when functional). Test the heater relay by checking for continuity when energized and verifying proper switching voltage. Replace components that fall outside manufacturer specifications.

Step 4: Check Battery and Charging System Health Perform a load test on both batteries and verify the alternator output (should be 13.8-14.4V at idle). On machines with extended service hours, battery degradation is a frequent culprit for voltage-related codes.

Professional Disclaimer: This guide provides general diagnostic procedures. Always consult the Hyundai service manual for your specific machine serial number and torque specifications. If you're uncomfortable with electrical diagnostics, contact a certified Hyundai heavy equipment technician to prevent further damage to electrical components.