What is Caterpillar Fault Code CID3573?

Caterpillar Fault Code CID3573 indicates a communication error or data link failure within the machine's Controller Area Network (CAN) bus system. This fault specifically signals that the Electronic Control Module (ECM) has detected an abnormal message or loss of communication from a critical component controller on the network.

The CAN bus serves as the central nervous system for modern Caterpillar excavators, allowing multiple electronic controllers to communicate and share operational data. CID3573 typically appears when the ECM cannot receive expected messages from controllers managing systems like the hydraulics, engine aftertreatment, or display modules. This communication breakdown can trigger protective modes that limit machine performance to prevent potential damage. For used excavators with aging electrical systems, this code often surfaces due to corrosion, wiring degradation, or intermittent connection issues that develop over thousands of operating hours.

Common Symptoms

When CID3573 is active, operators may experience:

• Warning lights illuminated on the instrument cluster, often accompanied by a check engine or diagnostic lamp
• Reduced engine power or derate mode, limiting RPM and hydraulic function speed
• Intermittent loss of display information, with gauges reading incorrectly or going blank
• Erratic hydraulic response or delayed reaction to joystick inputs
• Machine shutdown or failure to start in severe cases where critical communication is completely lost

Potential Causes

The most common technical reasons for CID3573 in used Caterpillar excavators include:

• Corroded or damaged connectors at controller junction points, especially in the engine bay or undercarriage areas exposed to moisture
• Wiring harness chafing at known rub points where harnesses contact the frame, boom cylinders, or cab mounting points
• Failed controller modules, particularly hydraulic or display controllers that may have water intrusion damage
• Poor ground connections causing voltage irregularities that disrupt CAN bus signal integrity
• ECM software glitches or outdated firmware requiring updates
• Aftermarket component interference from non-OEM parts that don't communicate properly on the network

How to Troubleshoot and Fix Code CID3573

Step 1: Connect Diagnostic Software Use Caterpillar Electronic Technician (Cat ET) diagnostic software to read active and logged faults. Identify which specific controller is failing to communicate by reviewing the fault details and associated Component Identifiers (CIDs).

Step 2: Perform Visual Harness Inspection Thoroughly inspect all wiring harnesses and connectors between the ECM and the identified failing controller. On used excavators, pay special attention to areas where harnesses route near moving parts, heat sources, or the undercarriage. Look for abraded insulation, crushed wires, corroded pins, or moisture in connector housings. Clean all connections with electrical contact cleaner and apply dielectric grease.

Step 3: Test CAN Bus Signal Integrity Using a digital multimeter, measure CAN High and CAN Low voltage at the suspect controller connector. You should see approximately 2.5V on both lines at rest, with differential voltage between 1.5-3.5V during communication. Resistance between CAN High and CAN Low should read approximately 60 ohms with controllers disconnected, indicating proper termination resistors.

Step 4: Check Power and Ground Circuits Verify the suspect controller receives proper battery voltage (typically 24V for larger excavators) and has a solid ground connection with less than 0.1 ohms resistance to chassis ground. Corroded ground straps are extremely common in used machines.

Step 5: Swap or Update Controllers If wiring tests pass, the controller itself may be faulty. Before replacing, attempt a software flash or firmware update through Cat ET, as outdated software can cause communication errors. If replacement is necessary, ensure you're using genuine Caterpillar parts programmed with the correct machine configuration.

Disclaimer: This guide provides general diagnostic information. Always consult the official Caterpillar service manual for your specific machine model and serial number. Complex electrical diagnostics may require professional technician assistance with specialized equipment.