Komatsu PC120-6 Fault Code E207: Complete Diagnostic Guide

What is Komatsu PC120-6 Fault Code E207?

Fault Code E207 indicates a malfunction in the hydraulic pump solenoid valve circuit, specifically detecting an abnormal electrical signal or open circuit in the pump control system. This code is triggered when the Electronic Control Module (ECM) detects voltage irregularities or communication failures with the hydraulic pump's proportional solenoid valve, which regulates pump displacement and system pressure.

For the PC120-6 model, this is critical because the pump solenoid directly controls hydraulic flow distribution to all working functions. When E207 activates, the ECM typically defaults to a low-power mode to prevent damage, severely limiting machine productivity and potentially causing complete hydraulic system shutdown.

Common Symptoms

• Significant loss of hydraulic power across all functions (boom, arm, bucket, swing)
• Erratic or sluggish hydraulic response, especially during combined operations
• Warning lamp illumination on the instrument panel with simultaneous alarm buzzer
• Machine entering derate mode, restricting engine RPM to approximately 1,500-1,800 range
• Intermittent operation where hydraulics work normally then suddenly lose power

Potential Causes

The E207 code typically stems from these issues commonly found in used PC120-6 excavators:

• Solenoid valve coil failure due to overheating or internal winding breakdown (resistance should measure 18-22 ohms)
• Wiring harness damage near the pump mounting area where vibration causes insulation wear and wire exposure
• Corroded or loose connector pins at the 12-pin pump solenoid connector, particularly from water infiltration
• ECM internal driver circuit failure, though less common than harness issues
• Damaged or pinched wiring along the chassis rail routing between ECM and hydraulic pump

How to Troubleshoot and Fix Code E207

Step 1: Visual Inspection Disconnect the battery ground. Locate the hydraulic pump solenoid connector on the pump's rear section. Inspect for corrosion, bent pins, oil contamination, or moisture. On used machines, check for harness wear points where wires contact the pump body or chassis.

Step 2: Electrical Testing Using a digital multimeter, measure solenoid coil resistance at the pump-side connector. Specification is 18-22 ohms at 20°C. Also check for continuity to ground—any reading below 10k ohms indicates insulation breakdown.

Step 3: Wiring Verification Trace the harness from ECM (located under the operator's seat) to the pump. Test supply voltage at the connector with ignition on—should read battery voltage (12V). Check ground circuit integrity (less than 1 ohm resistance to chassis ground).

Step 4: Component Replacement If resistance is out of specification, replace the proportional solenoid valve assembly (Komatsu part number 702-21-55901). If wiring shows damage, repair or replace the affected harness section, ensuring proper routing away from heat and moving components.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu PC120-6 service manual and consider professional diagnosis for complex electrical issues. Improper repairs may cause additional system damage.