What is Caterpillar Fault Code CID1735?

CID1735 indicates a communication error or data link failure within the Caterpillar electronic control system, specifically related to Controller Area Network (CAN) messaging between the Engine Control Module (ECM) and other machine controllers. This fault code appears when the ECM detects that expected data packets from connected controllers are missing, corrupted, or arriving outside acceptable timing parameters.

This code is critical for Caterpillar excavators because modern machines rely on constant communication between multiple electronic control units—including the hydraulic control module, monitor display, and transmission controller. When CID1735 activates, the machine may enter a protective mode that limits performance to prevent potential damage from uncoordinated system operation. For used excavators, this fault often stems from age-related deterioration of the electrical infrastructure rather than catastrophic component failure.

Common Symptoms

• Warning lights illuminating on the operator display, often accompanied by a "Communication Error" or "System Fault" message
• Reduced engine power or machine entering derate mode, limiting hydraulic functions and travel speed
• Intermittent loss of gauge readings on the monitor (fuel level, temperature, or hour meter flickering)
• Erratic hydraulic response or delayed reaction when operating joysticks and pedals
• Engine may start but immediately shut down or refuse to start altogether in severe cases

Potential Causes

The most common technical reasons for CID1735 in used Caterpillar excavators include:

• Damaged CAN bus wiring harness, particularly at known rub points near the swing bearing, boom cylinders, or engine firewall where cables experience constant flexing
• Corroded or loose connector pins on the ECM or auxiliary controllers, especially on machines operated in high-moisture or marine environments
• Failed terminating resistors within the CAN network, which are essential for proper signal integrity
• Faulty ECM or secondary controller with internal communication circuit failure
• Low voltage conditions from weak batteries or failing alternators, causing intermittent data transmission errors
• Aftermarket accessories improperly spliced into the CAN network without proper isolation

How to Troubleshoot and Fix Code CID1735

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 bulkheads or near moving components. On used excavators, check for abrasion marks, cracked insulation, or evidence of previous repairs with electrical tape. Disconnect and inspect all ECM connectors and related controller plugs for bent pins, green corrosion, or moisture intrusion.

Step 2: Check Power Supply and Ground Circuits Using a digital multimeter, verify that the ECM and all networked controllers receive proper voltage (typically 24V for larger Caterpillar excavators, 12V for smaller models). Check that battery voltage remains stable above 22V (or 11V for 12V systems) during cranking. Inspect all ground connections for tightness and clean metal-to-metal contact, as poor grounds frequently cause intermittent communication faults.

Step 3: Test CAN Bus Integrity Connect Caterpillar Electronic Technician (Cat ET) diagnostic software to access detailed fault information and active/inactive status. Use the software to monitor real-time CAN bus traffic and identify which specific controller is dropping communication. Check CAN High and CAN Low wire resistance between the ECM and suspect controllers—readings should show approximately 60 ohms with all controllers connected (indicating proper termination). Measure voltage between CAN High and CAN Low wires with key on, engine off—you should see approximately 2.5V at rest.

Step 4: Address Component-Specific Issues For used excavators, if wiring and voltage checks pass, suspect terminating resistor failure or internal controller faults. Check for aftermarket components that may have been improperly integrated into the network. Replace any corroded connectors with OEM-quality parts, and ensure proper dielectric grease application to prevent future corrosion. If a specific controller is identified as non-communicative, swap with a known-good unit to confirm before purchasing expensive replacement parts.

Disclaimer: This guide provides general diagnostic information for CID1735 on Caterpillar excavators. Electrical systems vary by specific model year and configuration. Always consult the official Caterpillar service manual for your exact machine serial number, and consider professional diagnostic assistance if you lack specialized tools or experience with heavy equipment electronics.