What is Case CX220C Fault Code 7602?

Fault Code 7602 on the Case CX220C excavator indicates a malfunction in the Auxiliary Hydraulic Circuit 1 (Aux 1) solenoid valve or its associated electrical circuit. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormal voltage, open circuit, or short circuit in the Aux 1 proportional solenoid valve wiring or the solenoid itself.

The Aux 1 circuit controls optional hydraulic attachments like breakers, grapples, or augers on the CX220C. When this code appears, the ECM cannot properly regulate hydraulic flow to auxiliary tools, directly impacting jobsite productivity. This fault is critical because it affects the machine's versatility and can indicate deeper electrical issues that may spread to other hydraulic control systems if left unaddressed.

Common Symptoms

When Code 7602 is active on your Case CX220C, operators typically experience:

• Auxiliary hydraulic function completely inoperative – attachments won't respond to joystick commands
• Intermittent operation of Aux 1 circuit, especially when machine vibrates or operates on uneven terrain
• Warning light illuminated on the instrument cluster with fault code displayed on monitor
• Reduced hydraulic flow to auxiliary attachments, causing sluggish or weak performance
• ECM may log multiple instances of the code during a single operating cycle

Potential Causes

The most common technical causes for Code 7602 in used CX220C excavators include:

• Damaged or corroded wiring harness at the solenoid connector – common wear point where harness rubs against the boom structure
• Failed Aux 1 proportional solenoid valve due to contaminated hydraulic oil causing internal coil failure
• Connector pin corrosion or moisture intrusion at the 6-pin Deutsch connector near the control valve block
• Broken or frayed wires inside the main harness between the cab and valve bank (known issue on high-hour machines)
• ECM internal driver circuit failure (rare, but possible on machines with 8,000+ hours)
• Voltage supply issues from the machine's main power distribution, affecting multiple circuits

How to Troubleshoot and Fix Code 7602

Step 1: Visual Inspection Begin by inspecting the wiring harness running from the cab to the auxiliary control valve block on the main hydraulic manifold. Look for obvious damage, particularly where the harness passes over the boom pivot point. Check the Deutsch connector at the solenoid for corrosion, bent pins, or oil contamination. On used excavators, this connector often shows green corrosion due to years of exposure.

Step 2: Electrical Testing Using a digital multimeter, disconnect the solenoid connector and measure resistance across the solenoid coil terminals. A healthy Aux 1 solenoid should read approximately 8-12 ohms. Readings below 5 ohms indicate a short circuit; infinite resistance means an open circuit. Next, check for supply voltage at the harness side connector with the ignition on – you should see 12-14 volts DC. Use CNH EST diagnostic software (Case's factory tool) to command the solenoid on/off and monitor real-time voltage.

Step 3: Component Replacement and Verification If resistance is out of specification, replace the Aux 1 proportional solenoid valve (Case Part #87480444 or equivalent). Before installation, clean the valve mounting surface and apply dielectric grease to connector pins to prevent future corrosion. If wiring shows damage, repair using weatherproof solder connections and heat shrink tubing rated for hydraulic environments. After repairs, clear the code using diagnostic software and cycle the auxiliary function 20-30 times while monitoring for code recurrence.

Critical for used machines: Always inspect the entire harness routing for chafe points against metal edges, and secure with new zip ties or protective loom. Check hydraulic oil quality – contaminated oil accelerates solenoid failures.

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Disclaimer: This guide provides general troubleshooting information for Case CX220C excavators. Hydraulic and electrical systems operate under high pressure and voltage. Always consult your machine's service manual and consider professional diagnostic assistance for complex repairs. Improper repairs may cause equipment damage or safety hazards.