What is Komatsu PC200LC-7 Fault Code E-18?

Fault Code E-18 on the Komatsu PC200LC-7 indicates a malfunction in the engine pre-heating system, specifically related to the glow plug circuit or its control relay. This code is triggered when the Electronic Control Module (ECM) detects abnormal resistance, voltage, or circuit continuity in the pre-heating system during startup diagnostics.

The glow plug system is critical for cold-start performance on the PC200LC-7's SAA6D102E-2 diesel engine. When this system fails, the engine struggles to ignite fuel efficiently during cold conditions, leading to hard starts, excessive white smoke, and increased wear on starter components. For used excavators operating in colder climates, a functional pre-heating system is essential to prevent catastrophic starter motor failure and maintain reliable daily operation.

Common Symptoms

• Hard starting or extended cranking time, especially in temperatures below 50°F (10°C)
• Excessive white or gray smoke during cold starts due to incomplete combustion
• Glow plug indicator light remains illuminated or flashes on the instrument panel
• ECM warning light activates, potentially limiting engine power output
• Rough idle immediately after cold starts until engine reaches operating temperature

Potential Causes

The E-18 code on used PC200LC-7 excavators typically stems from age-related electrical deterioration. The most common causes include:

• Failed glow plugs (one or multiple) due to carbon buildup or element burnout after 3,000+ operating hours
• Glow plug relay failure causing open or shorted circuit conditions
• Corroded or damaged wiring harness connections at the glow plug connector junction, particularly where harnesses run along the valve cover
• Faulty ECM glow plug control output due to moisture intrusion or internal circuit board degradation
• Poor ground connections at the engine block ground strap, common on machines with 5,000+ hours

How to Troubleshoot and Fix Code E-18

Step 1: Visual Inspection
Inspect all glow plug harness connections for corrosion, oil contamination, or physical damage. On used PC200LC-7s, check where the harness runs alongside the valve cover—this is a known rub point. Clean all connections with electrical contact cleaner and apply dielectric grease.

Step 2: Test Glow Plugs
Using a digital multimeter, measure resistance across each glow plug terminal to ground with plugs installed. Specification is typically 0.5-2.0 ohms. Replace any plug reading open circuit (infinite resistance) or below 0.3 ohms (shorted).

Step 3: Check Glow Plug Relay
Locate the glow plug relay in the main fuse box. With ignition on (engine off), you should hear an audible click and measure battery voltage (12V) at the relay output terminal during the pre-heat cycle (15-30 seconds). No voltage indicates relay failure.

Step 4: Verify ECM Control Signal
Using Komatsu KOMTRAX diagnostic software or an aftermarket scan tool, monitor the ECM's glow plug control output signal. The ECM should command the relay closed during pre-heat cycles. If the command is present but no relay action occurs, verify ground circuit continuity.

Step 5: Inspect Wiring Harness
For machines with high operating hours, perform a continuity test on all glow plug harness wiring from the relay to each plug. Repair or replace any wiring showing high resistance (above 0.5 ohms) or intermittent continuity.

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Disclaimer: This guide provides general troubleshooting procedures. Always consult the Komatsu PC200LC-7 service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs may void warranties or cause additional damage.