What is Caterpillar Fault Code CID1335?

Caterpillar Fault Code CID1335 indicates a communication error or data link failure within the machine's Controller Area Network (CAN) bus system. This code typically appears when the Electronic Control Module (ECM) loses communication with one or more critical controllers, sensors, or displays on the machine network.

The CAN bus serves as the central nervous system for modern Caterpillar excavators, allowing multiple electronic components to exchange data continuously. When CID1335 triggers, it signals that a controller has stopped responding or is sending corrupted data packets. This is particularly critical because the ECM relies on real-time information from hydraulic controllers, transmission modules, and monitoring systems to optimize performance and protect engine components. On used excavators, this fault can indicate deteriorating wiring harnesses, corroded connectors, or failing control modules that have exceeded their service life.

Common Symptoms

• Warning lights illuminate on the instrument cluster, often accompanied by a "Check Engine" or communication error message on the monitor display
• Derated engine performance with reduced power output or limited RPM range as the ECM enters protective mode
• Intermittent gauge failures where the operator panel shows erratic readings or complete loss of display functions
• Hydraulic system irregularities including sluggish response or unexpected function limitations
• Difficulty starting or the engine may start then immediately shut down due to safety protocols

Potential Causes

The most common causes of CID1335 on used Caterpillar excavators include:

• Damaged or corroded wiring harness connections, especially at known rub points near the swing bearing, boom pivot, or along the undercarriage where vibration and moisture exposure occur
• Failed controller modules such as the hydraulic control unit, display panel, or secondary ECM that has stopped communicating
• Loose or oxidized ground connections that disrupt the CAN bus voltage reference
• Water intrusion into connector bodies, particularly common on machines with compromised seals or stored outdoors
• ECM software corruption or compatibility issues after component replacement without proper programming
• Damaged CAN bus termination resistors causing signal reflection and communication breakdown

How to Troubleshoot and Fix Code CID1335

Step 1: Connect Diagnostic Software Use Caterpillar Electronic Technician (Cat ET) diagnostic software to read active and logged fault codes. Document all CID codes present and note which specific controller is reporting the communication failure. Check the fault occurrence pattern—intermittent faults suggest wiring issues, while constant faults indicate complete component failure.

Step 2: Perform Visual Harness Inspection Physically inspect the entire main wiring harness, paying special attention to areas where cables flex or contact metal surfaces. On used excavators, check connector pins for corrosion, bent terminals, or moisture. Disconnect and reconnect each connector along the CAN bus circuit, applying dielectric grease to protect against future oxidation.

Step 3: Test CAN Bus Voltage and Resistance Using a digital multimeter, measure CAN High and CAN Low voltage at the diagnostic connector. You should see approximately 2.5V on each line with the key on, engine off. Measure resistance between CAN High and CAN Low—it should read between 55-65 ohms with termination resistors intact. Values outside this range indicate open circuits, short circuits, or missing termination.

Step 4: Isolate the Faulty Component Systematically disconnect controllers one at a time while monitoring the diagnostic software. When the communication error clears after disconnecting a specific module, you've identified the problematic component. Before replacing any controller, clean all connector contacts thoroughly and retest—many "failed" modules on used machines simply have dirty connections.

Step 5: Verify Repair and Clear Codes After addressing wiring issues or replacing components, clear all fault codes through Cat ET and operate the machine through a complete work cycle. Monitor for code reoccurrence and verify all systems respond normally.

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Disclaimer: This guide provides general troubleshooting information for Caterpillar fault code CID1335. Always consult the specific service manual for your excavator model and serial number. If you lack experience with electrical diagnostics or Cat ET software, consult a certified Caterpillar technician to prevent further damage to electronic systems.