What is Komatsu PC160LC-7 Fault Code E-21?

Fault Code E-21 on the Komatsu PC160LC-7 indicates a malfunction in the hydraulic pump delivery system, specifically relating to the pump flow control solenoid valve or its associated circuitry. This code is triggered when the Electronic Control Module (ECM) detects an abnormal electrical signal or operational discrepancy in the pump's proportional control system.

The PC160LC-7 utilizes a sophisticated closed-center hydraulic system with electronically-controlled variable displacement pumps. The pump flow control solenoid regulates hydraulic flow based on operator inputs and load demands. When E-21 appears, the system cannot properly modulate pump output, directly impacting machine productivity and potentially causing component damage. This fault is particularly critical because it affects the excavator's ability to deliver precise hydraulic power to the boom, arm, bucket, and swing functions.

Common Symptoms

When Code E-21 is active, operators typically experience:

• Reduced hydraulic power across all functions, with noticeably slower cycle times for boom, arm, and bucket operations
• Erratic or jerky movements during combined functions (e.g., simultaneous swing and boom operation)
• Warning light illumination on the instrument cluster, often accompanied by an audible alarm
• Inconsistent engine response to hydraulic load changes, with possible engine rpm fluctuations
• Complete loss of hydraulic function in severe cases, rendering the machine inoperable

Potential Causes

The most common technical causes for E-21 on used PC160LC-7 excavators include:

• Failed pump control solenoid valve due to internal coil burnout or mechanical wear (common after 6,000+ operating hours)
• Damaged wiring harness between the ECM and pump solenoid, particularly at known rub points near the hydraulic pump mounting area and along the main frame rail
• Corroded or loose electrical connectors at the solenoid valve connection point, especially on machines operated in wet or marine environments
• ECM internal faults or corrupted software parameters affecting pump control output signals
• Low system voltage from failing alternator or weak batteries causing insufficient solenoid activation current
• Hydraulic contamination causing the solenoid spool to stick or bind internally

How to Troubleshoot and Fix Code E-21

Step 1: Initial Diagnostic Scan Connect a Komatsu diagnostic tool (KOMTRAX or compatible scan tool) to retrieve active and stored fault codes. Document freeze-frame data showing operating conditions when E-21 triggered. Clear codes temporarily and attempt to replicate the fault under controlled conditions to determine if it's intermittent or constant.

Step 2: Electrical System Verification Using a digital multimeter, measure battery voltage (should be 12.5-13V key-on, 13.8-14.4V running). Inspect the pump solenoid connector (typically located on the main hydraulic pump body) for corrosion, bent pins, or moisture intrusion—common issues on used excavators. Check connector terminal resistance; clean contacts with electrical contact cleaner and apply dielectric grease.

Step 3: Solenoid Resistance Testing Disconnect the pump control solenoid connector and measure coil resistance across the solenoid terminals. Specification for the PC160LC-7 pump solenoid is typically 3-6 ohms at 20°C. Readings outside this range indicate solenoid failure. Also check for continuity to ground (should be infinite resistance/open circuit).

Step 4: Wiring Harness Inspection Physically trace the solenoid harness from the ECM to the pump, paying special attention to areas where the harness contacts metal edges, particularly near the pump mounting bracket and along the right-side frame rail. On used machines, insulation wear from vibration is common. Look for chafed wires, exposed copper, or evidence of previous repairs with electrical tape.

Step 5: Signal Testing (Advanced) With the ignition on and engine off, use a multimeter to backprobe the ECM connector and measure the control signal voltage to the solenoid (typically 0-12V PWM signal). If signal is present at ECM but not at solenoid, wiring fault is confirmed. If no signal from ECM, suspect ECM failure or software issue requiring authorized Komatsu diagnostics.

Step 6: Component Replacement If testing confirms solenoid failure, replace with genuine Komatsu parts (part number specific to PC160LC-7E pump assembly). Aftermarket solenoids often have incorrect resistance specifications. After replacement, perform hydraulic system function tests and verify code clears permanently.

Crucial for Used Excavators: Before replacing any components, thoroughly inspect for evidence of previous repairs, improper maintenance, or hydraulic contamination. Check hydraulic oil condition—metal particles or varnish indicate internal pump wear that may cause recurring solenoid failures. Verify oil filter hasn't been neglected, as bypass conditions can send contamination directly to sensitive control valves.

---

Disclaimer: This guide provides general troubleshooting information for educational purposes. Hydraulic systems operate under extreme pressure and electrical diagnostics require proper training. Always consult the official Komatsu service manual for your specific machine serial number and consider professional assistance from certified Komatsu technicians for complex repairs. Improper diagnosis or repair may result in equipment damage, personal injury, or warranty issues.