What is Caterpillar Fault Code CID1953?

CID1953 indicates a communication error or data link failure within the Caterpillar CAN (Controller Area Network) system, specifically related to a missing or intermittent message from a critical electronic control module. This fault occurs when the primary ECM (Engine Control Module) fails to receive expected data packets from connected components like the hydraulic control system, display monitor, or auxiliary control modules within the specified timeframe.

This code is critical for Caterpillar excavators because the CAN Bus serves as the central nervous system for machine diagnostics, performance monitoring, and coordinated control between engine, hydraulics, and implement functions. When communication breaks down, the machine may enter derate mode or limit certain functions to protect components from uncoordinated operation. For used excavators, this fault often stems from aging wiring harnesses, corroded connectors, or failing control modules that have accumulated thousands of operating hours.

Common Symptoms

• Warning lamp illumination on the instrument cluster with reduced engine power or hydraulic response
• Intermittent loss of display functions or erratic gauge readings on the monitor panel
• Unexpected derating where engine RPM is limited to 1500-1800 range regardless of throttle input
• Hydraulic system sluggishness or failure of specific functions like swing or auxiliary circuits
• Intermittent code appearance that clears and returns, especially when machine vibrates or operates in cold conditions

Potential Causes

• Damaged or corroded CAN Bus wiring harness, particularly at flex points near the swing bearing or boom pivot areas where cables experience repeated bending
• Loose or corroded electrical connectors at control modules, especially the 9-pin or 37-pin Deutsch connectors common in Caterpillar systems
• Failed electronic control module (hydraulic controller, monitor ECM, or aftertreatment control unit) no longer transmitting on the network
• Faulty terminating resistors (120-ohm resistors) at CAN Bus endpoints causing signal reflection and data corruption
• Water intrusion into junction boxes or control module enclosures, common in used machines with compromised seals
• Improper aftermarket installations or modifications that created short circuits or incorrect CAN Bus tap points

How to Troubleshoot and Fix Code CID1953

Step 1: Connect Diagnostic Software Use Caterpillar Electronic Technician (Cat ET) software with a communication adapter to identify which specific module is not communicating. Navigate to the "Configuration" screen to see all modules that should be present versus those actively responding. Document the missing module identifier.

Step 2: Inspect Physical Connections Locate the non-communicating module and thoroughly inspect its wiring harness and connectors. For used excavators, pay special attention to harness routing near hydraulic lines where heat damage occurs, and at articulation points where wire insulation may be worn through. Check for:

• Green corrosion on connector pins (indicates moisture intrusion)
• Bent or pushed-back pins inside connectors
• Chafed wiring insulation at cable ties or brackets

Step 3: Perform Electrical Testing With the key off and connectors separated, use a digital multimeter to check CAN Bus continuity. Measure resistance between CAN High and CAN Low terminals at the network backbone—should read approximately 60 ohms with both terminating resistors in place. Test individual module connectors for:

• Ground integrity (less than 1 ohm to chassis ground)
• Power supply voltage (typically 8-14 VDC at module power pins with key on)
• CAN signal wire continuity from module connector back to ECM

Step 4: Check Terminating Resistors and Replace Failed Components Verify both 120-ohm terminating resistors are present at network endpoints. If electrical tests pass but communication fails, the control module itself has likely failed—common in machines with 8,000+ hours. For used excavators, always clean and apply dielectric grease to all connectors during reassembly to prevent future corrosion issues.

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Disclaimer: This guide provides general troubleshooting information for CID1953 on Caterpillar excavators. Always consult the machine's specific service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs can cause additional system damage or safety hazards.