What is Caterpillar Fault Code CID1672?

Caterpillar CID1672 indicates a communication error or data link failure within the machine's Controller Area Network (CAN) bus system. This fault code specifically signals that the Electronic Control Module (ECM) has detected an interruption, abnormal message transmission, or complete loss of communication between critical electronic controllers on the excavator.

The CAN bus serves as the central nervous system for modern Caterpillar excavators, allowing the engine controller, hydraulic controller, display monitor, and other electronic modules to exchange real-time operational data. When CID1672 appears, it means one or more controllers cannot properly communicate, which directly impacts the machine's ability to coordinate engine performance, hydraulic functions, and operator interface systems. For used excavators, this code is particularly concerning because it can indicate aging wiring harnesses, corroded connector pins, or failing control modules that have accumulated wear over thousands of operating hours.

Common Symptoms

• Warning lights illuminated on the operator display, often with reduced functionality or blank screens showing "Communication Error"
• Derated engine performance or the machine entering limp mode, limiting RPM and hydraulic power output
• Intermittent or complete loss of gauge cluster functions, including fuel level, temperature, and hour meter readings
• Erratic hydraulic behavior such as inconsistent swing speed, boom response delays, or attachment control issues
• Diagnostic software connection failures when attempting to read fault codes or perform system checks

Potential Causes

• Damaged or corroded CAN bus wiring harness, especially at known rub points near the engine compartment, swing bearing area, or along the boom structure where cables flex repeatedly
• Loose or oxidized connector pins at module connection points, particularly common in used machines exposed to moisture, dirt, and vibration
• Failed Electronic Control Module (ECM) or other controller units due to age-related component degradation or voltage spikes
• Faulty terminating resistors on the CAN bus network causing signal reflection and communication breakdown
• Low battery voltage or poor ground connections affecting the stability of electronic communications throughout the system
• Aftermarket accessory installations that improperly tap into the CAN network, introducing electrical noise or short circuits

How to Troubleshoot and Fix Code CID1672

Step 1: Visual Inspection of Wiring and Connectors Begin by thoroughly inspecting all CAN bus harness routing, paying special attention to areas where cables pass through metal frames, near hot engine components, or at articulation points. On used excavators, check for chafed insulation, pinched wires, or evidence of previous repairs using electrical tape. Disconnect and inspect all controller connectors, looking for bent pins, corrosion (green or white deposits), moisture intrusion, or burnt contacts. Clean connectors with electrical contact cleaner and apply dielectric grease before reconnection.

Step 2: Electrical Testing with Multimeter Using a digital multimeter (DMM), verify battery voltage is consistently above 12.5V (24V systems: 25V) and check all ground connections for resistance below 0.5 ohms. Locate the CAN High (CAN-H) and CAN Low (CAN-L) wires—typically a twisted pair with yellow and green insulation on Caterpillar machines. With the key on and engine off, measure voltage between CAN-H and ground (should read approximately 2.5-3.5V) and CAN-L and ground (approximately 1.5-2.5V). Measure resistance between CAN-H and CAN-L with all modules disconnected; you should read approximately 60 ohms, indicating proper terminating resistors are present.

Step 3: Advanced Diagnostics with Caterpillar ET Software Connect Caterpillar Electronic Technician (ET) diagnostic software to identify which specific controller is dropping off the network. The software will show active and inactive modules, helping isolate whether the engine ECM, hydraulic controller, monitor, or another device is causing the communication failure. For used machines, perform a parameter comparison against factory specifications to identify modules with outdated firmware or configuration errors. Check for multiple simultaneous fault codes that may point to a specific failed controller rather than wiring issues.

Step 4: Component Replacement and Verification If diagnostics identify a specific failed component, replace the faulty controller, damaged harness section, or corroded connectors as needed. On used excavators, consider replacing entire harness sections rather than attempting splice repairs in high-flex areas, as temporary fixes often fail prematurely. After repairs, clear all fault codes, cycle the key, and operate the machine through full range of motion while monitoring for code recurrence. Verify all system functions return to normal and perform a final scan with Cat ET software to confirm stable communication across all modules.

---

Disclaimer: This guide provides general troubleshooting information for Caterpillar CID1672. Electrical system diagnostics require proper training and safety precautions. Always consult the official Caterpillar service manual for your specific model and consider professional diagnostic services for complex electronic issues, especially when working with used equipment that may have undocumented modifications.