What is Case CX220C Fault Code 87?

Fault Code 87 on the Case CX220C excavator indicates a Swing Motor Solenoid Valve Circuit malfunction, specifically detecting an open circuit or short circuit in the electrical system controlling the swing motor's hydraulic solenoid valve. This diagnostic trouble code (DTC) is generated by the machine's Electronic Control Module (ECM) when it detects abnormal voltage or current readings outside the manufacturer's specified parameters (typically 10-14 volts during operation).

This code is critical because the swing motor solenoid controls hydraulic flow to the upper structure's rotation system. When this circuit fails, the excavator's ability to rotate smoothly—or at all—becomes compromised, directly impacting productivity and potentially creating safety hazards on job sites. For used CX220C models, this code often surfaces due to age-related electrical degradation rather than component failure.

Common Symptoms

• Swing function becomes erratic or completely inoperative, with the upper structure failing to rotate or moving intermittently
• Warning light or fault indicator illuminates on the instrument cluster, often accompanied by an audible alarm
• Reduced swing speed or loss of swing power, even when other hydraulic functions operate normally
• ECM may enter derate mode, limiting engine RPM to protect the hydraulic system from damage
• Hydraulic oil temperature increase due to improper valve operation causing flow restrictions

Potential Causes

The most common technical causes for Code 87 on used Case CX220C excavators include:

• Damaged wiring harness between the ECM and swing motor solenoid valve, particularly at flex points near the center joint where constant rotation causes wire fatigue
• Corroded or loose electrical connectors at the solenoid valve plug, especially on machines operating in wet or corrosive environments
• Failed swing motor solenoid coil, which typically shows resistance outside the 8-15 ohm specification range
• Shorted or open circuits in the valve control wiring due to chafing against metal edges or pinch points
• ECM internal fault (less common) affecting the output driver circuit for the swing solenoid
• Voltage supply issues from the machine's main electrical system causing insufficient power to the solenoid circuit

How to Troubleshoot and Fix Code 87

Step 1: Initial Inspection and Code Verification Connect a Case diagnostic software tool (ServiceMaster or compatible interface) to retrieve active and stored codes. Verify Code 87 is current, not historical. With the ignition on and engine off, visually inspect the swing motor solenoid valve located on the swing motor assembly. Check for obvious damage, disconnected connectors, or oil contamination on electrical components.

Step 2: Electrical Testing of Solenoid Circuit Disconnect the solenoid valve connector and measure coil resistance using a digital multimeter. Specifications should read between 8-15 ohms. If readings show infinite resistance (open circuit) or near-zero (short circuit), replace the solenoid valve. Next, check for supply voltage at the harness connector with ignition on—should read approximately 12 volts. No voltage indicates a wiring or ECM output problem.

Step 3: Harness and Connector Inspection For used excavators, this is crucial: trace the entire wiring harness from the ECM (located in the cab) through the center joint to the swing motor. Look for worn insulation, especially where harnesses pass through grommets or contact metal edges. Inspect the center joint rotary connector for corrosion or damaged pins—a common failure point on older CX220C models. Clean all connectors with electrical contact cleaner and apply dielectric grease.

Step 4: ECM Testing and Replacement If wiring and solenoid test good, suspect ECM failure. Using diagnostic software, perform an output test to command the swing solenoid on/off while monitoring voltage at the connector. If the ECM cannot switch the circuit, internal driver failure is indicated and ECM replacement is necessary.

Professional Disclaimer: While these procedures provide guidance for diagnosing Code 87, electrical system repairs should be performed by qualified technicians with proper Case service documentation. Incorrect diagnosis can lead to expensive component replacement or additional machine damage. Always consult the official Case service manual for your specific serial number range.