What is Komatsu PC200LC-7 Fault Code H-19?

Fault Code H-19 on the Komatsu PC200LC-7 indicates a hydraulic oil temperature sensor circuit malfunction or abnormally high hydraulic oil temperature reading. This code is triggered when the machine's Electronic Control Module (ECM) detects either an electrical fault in the temperature sensor circuit or a genuine overheating condition in the hydraulic system exceeding approximately 110-120°C (230-248°F).

This fault code directly affects the hydraulic system monitoring on the PC200LC-7, which is critical for preventing catastrophic damage to hydraulic pumps, motors, and cylinder seals. When hydraulic oil overheats or the sensor fails, the machine loses its ability to protect expensive hydraulic components from thermal breakdown, potentially leading to thousands of dollars in repair costs on used excavators where components may already show wear.

Common Symptoms

When H-19 is active on your Komatsu PC200LC-7, operators typically experience:

• Hydraulic oil temperature warning light illuminated on the monitor panel (red or amber depending on severity)
• Reduced hydraulic system performance or automatic speed derate to protect components
• Audible alarm sounding intermittently or continuously
• Loss of power during high-demand operations like digging or lifting heavy loads
• Sluggish hydraulic response across boom, arm, bucket, and swing functions

Potential Causes

The most common technical causes for H-19 on used PC200LC-7 excavators include:

• Failed hydraulic oil temperature sensor – The thermistor-type sensor degrades over time, particularly on machines with 5,000+ hours
• Damaged or corroded sensor wiring harness – Exposed wiring near the hydraulic tank often suffers from abrasion or moisture intrusion
• Genuine hydraulic oil overheating – Caused by low oil levels, contaminated hydraulic oil, plugged oil cooler fins, or failing cooling fan
• Poor electrical connections at the sensor connector or ECM terminals due to corrosion or vibration damage
• ECM internal fault – Rare, but can occur in older machines exposed to harsh environments

How to Troubleshoot and Fix Code H-19

Step 1: Visual Inspection Locate the hydraulic oil temperature sensor mounted on the hydraulic tank (typically driver's side near the oil cooler). Inspect the sensor connector for corrosion, damaged pins, or loose connections. On used excavators, carefully examine the wiring harness for abrasion points where it contacts metal surfaces or moves with the upper structure.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At room temperature (20°C/68°F), the sensor should read approximately 2,000-3,000 ohms. Check the sensor circuit voltage at the ECM connector—expect around 5V reference voltage from the ECM. If voltage is absent, suspect harness breaks or ECM issues.

Step 3: Physical Verification Check actual hydraulic oil temperature using an infrared thermometer at the tank. If oil genuinely exceeds 100°C (212°F), inspect the hydraulic oil cooler for blockages, verify cooling fan operation, check hydraulic oil level, and examine oil condition for contamination or degradation.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu temperature sensor (Part #7861-93-3320 or equivalent). Clear the fault code using Komatsu diagnostic software (KOMTRAX) or a compatible scanner, then verify normal operation under load.

Disclaimer: This guide provides general troubleshooting information. Always consult your Komatsu service manual and consider professional diagnostic assistance for complex electrical issues on used excavators.