Why Won’t the Komatsu PC200-8 Start After Overhaul

[MikePhua]

The PC200-8 and Its Electronic Complexity
The Komatsu PC200-8 hydraulic excavator is part of Komatsu’s Dash-8 series, launched in the mid-2000s to meet Tier 3 emissions standards and improve fuel efficiency. With an operating weight around 20 metric tons and powered by a Komatsu SAA6D107E-1 engine, the PC200-8 was designed for general excavation, roadwork, and utility trenching. Komatsu, founded in 1921 in Japan, has long been a leader in integrating electronic control systems into heavy equipment. The PC200-8 features a full electronic engine management system, CAN bus diagnostics, and multiple sensors that monitor fuel, air, and hydraulic systems.
While these systems improve performance and emissions, they also introduce complexity—especially when troubleshooting post-overhaul issues.
Error Code E15 CA428 and Its Implications
One common issue after engine overhaul is the appearance of error code E15 CA428. This code typically indicates a high signal from the Water-In-Fuel (WIF) sensor. The WIF sensor is mounted on the fuel filter or separator and detects the presence of water in diesel fuel. Water contamination can cause injector damage, poor combustion, and engine stalling.
Terminology:

• WIF Sensor: A sensor that detects water in the fuel system and sends a signal to the ECU.
  
• ECU (Electronic Control Unit): The onboard computer that manages engine and hydraulic functions.
  
• CAN Bus: A communication protocol used to link sensors and controllers in modern machinery.
  

However, the presence of this error code does not necessarily prevent the engine from starting. In most cases, the engine will still crank and run, albeit with reduced performance or warning indicators.
Post-Overhaul Start Failures and Diagnostic Pathways
When a PC200-8 fails to start after an overhaul, and injectors have been serviced, the issue often lies in electrical connections, sensor feedback, or fuel delivery. The following diagnostic steps are recommended:

• Check all wiring harnesses for loose connectors, corrosion, or pin damage—especially around the ECU and injector plugs.
  
• Inspect the WIF sensor and its wiring. A shorted or open circuit can trigger false readings.
  
• Verify fuel pressure at the common rail. Use a diagnostic tool to confirm that the rail pressure meets starting thresholds (typically above 4,000 psi).
  
• Confirm that the crankshaft and camshaft position sensors are properly aligned and connected.
  
• Scan the ECU for additional fault codes beyond CA428. Sometimes multiple errors are masked by a dominant code.
  

In one case, a technician in Queensland discovered that the WIF sensor had been damaged during filter replacement. The sensor was sending a constant high signal, which confused the ECU and prevented proper fuel mapping. Replacing the sensor resolved the issue immediately.
Sensor Logic and ECU Behavior
The Komatsu ECU uses sensor logic to determine whether conditions are safe for engine start. If a critical sensor—such as the WIF, fuel pressure, or crank position sensor—sends an out-of-range signal, the ECU may inhibit starting to protect the engine.
Sensor hierarchy:

• Crankshaft Position Sensor: Required for ignition timing
  
• Fuel Rail Pressure Sensor: Required for injector activation
  
• WIF Sensor: Advisory only, does not block starting unless paired with other faults
  

Terminology:

• Fuel Mapping: The ECU’s control of fuel injection timing and quantity based on sensor input.
  
• Out-of-Range Signal: A sensor reading that falls outside expected parameters, triggering a fault.
  

In 2022, a fleet in Alberta reported multiple PC200-8 units failing to start after cold-weather overhauls. The root cause was condensation in the fuel tanks triggering WIF errors. After draining the tanks and replacing the sensors, all units returned to service.
Injector Service and Calibration Considerations
Servicing injectors on the PC200-8 requires precise calibration. Each injector has a trim code that must be entered into the ECU to ensure correct fuel delivery. Failure to input these codes can result in poor starting, misfires, or excessive smoke.
Injector service checklist:

• Verify that all six injectors are seated properly and torqued to spec
  
• Input trim codes using Komatsu’s diagnostic software
  
• Check for fuel leaks at the rail and return lines
  
• Perform a cylinder balance test to confirm even firing
  

Terminology:

• Trim Code: A calibration value unique to each injector, used by the ECU to adjust fuel delivery.
  
• Cylinder Balance Test: A diagnostic procedure to measure power output from each cylinder.
  

A contractor in Oregon reported that his PC200-8 wouldn’t start after injector replacement. The injectors were installed correctly, but the trim codes were not entered. Once programmed, the engine started and ran smoothly.
Recommendations for Field Technicians
To avoid post-overhaul start failures, technicians should:

• Always scan the ECU before and after service to identify hidden faults
  
• Replace sensors that show erratic readings, even if they don’t block starting
  
• Use dielectric grease on connectors to prevent moisture intrusion
  
• Keep a log of injector trim codes and sensor replacements for future reference
  

In addition, it’s wise to carry spare WIF sensors and fuel pressure sensors when servicing machines in remote or high-humidity environments.
Conclusion
The Komatsu PC200-8 is a powerful and efficient excavator, but its electronic systems demand precision during overhaul and diagnostics. Error code E15 CA428 points to a water-in-fuel sensor issue, which may not block starting but can confuse the ECU if paired with other faults. By understanding the logic behind sensor inputs, verifying injector calibration, and inspecting wiring thoroughly, technicians can resolve start failures and restore the machine to full operation. In today’s data-driven equipment world, mastering these systems is as essential as turning a wrench.