Komatsu PC650-8R Fault Code CA153: Complete Diagnostic Guide

What is Komatsu PC650-8R Fault Code CA153?

Fault Code CA153 indicates a malfunction in the Engine Control Module (ECM) communication circuit with the hydraulic pump control system. Specifically, this code triggers when the ECM detects an abnormal signal or loss of communication with the pump flow control solenoid valve or its associated wiring harness.

This code is critical for the PC650-8R because it directly affects the machine's ability to regulate hydraulic pump output based on engine load conditions. When communication fails, the excavator may default to a reduced performance mode to prevent potential damage to the hydraulic system or engine. For used excavators, this fault often indicates age-related deterioration in electrical connections or component wear that compromises signal integrity.

Common Symptoms

When Code CA153 is active, operators typically experience:

• Reduced hydraulic power across all functions, with noticeably slower cycle times
• Engine warning light illuminated on the instrument cluster (amber or red depending on severity)
• Erratic pump response where hydraulic flow doesn't match joystick input smoothly
• Intermittent loss of power that may come and go with machine vibration or temperature changes
• Error message displayed on the monitor panel indicating "Pump Control System Fault"

Potential Causes

The most common technical causes for CA153 on used PC650-8R excavators include:

• Corroded or loose connector pins at the pump control solenoid valve (C-connector behind pump assembly)
• Damaged wiring harness due to rubbing against the pump mounting bracket—a known wear point on this model
• Failed pump flow control solenoid valve with internal coil resistance outside specification (should read 8-12 ohms)
• ECM internal fault affecting the output driver circuit for pump control
• Voltage supply issues from the main power harness, particularly at splice points near the battery box
• Contaminated hydraulic oil causing solenoid valve sticking and electrical feedback errors

How to Troubleshoot and Fix Code CA153

Step 1: Visual Inspection Begin by inspecting the wiring harness running from the ECM to the hydraulic pump. On used excavators, check specifically where the harness passes near the pump mounting bracket and engine block for abrasion damage. Examine all connector pins for corrosion, bent terminals, or oil contamination. Clean connectors with electrical contact cleaner and apply dielectric grease.

Step 2: Electrical Testing Using a digital multimeter, measure the solenoid valve resistance by disconnecting the connector and testing across the solenoid terminals (should read 8-12 ohms at 20°C). Check for voltage supply at the connector with ignition on—you should see battery voltage (24V) on the power pin. Test for continuity in the ground circuit back to the ECM.

Step 3: Advanced Diagnostics Connect Komatsu KOMTRAX diagnostic software or a compatible scan tool to monitor live data from the pump control circuit. Observe the duty cycle percentage commanded by the ECM versus actual solenoid response. If communication is completely absent, suspect ECM internal failure. For intermittent codes on used machines, perform a wiggle test on harnesses while monitoring for signal dropout.

Step 4: Component Replacement If testing confirms solenoid failure, replace the pump flow control valve assembly (Part #: 702-21-55901). When replacing components on used excavators, always inspect mating surfaces for corrosion and replace O-rings and seals to prevent future contamination issues.

---

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional assistance from certified Komatsu technicians for complex electrical diagnostics or ECM replacement procedures.