Caterpillar Excavator Fault Code EID1718: Complete Diagnostic Guide

What is Caterpillar Fault Code EID1718?

Fault Code EID1718 indicates a Secondary Steering Control System malfunction, specifically detecting an abnormal signal or voltage from the secondary steering pressure sensor or its associated circuit. This code is part of Caterpillar's Electronic Technician (ET) diagnostic system and directly affects machines equipped with secondary steering or backup steering control systems.

The secondary steering system serves as a critical backup for the primary hydraulic steering circuit on Caterpillar excavators and wheel loaders. When EID1718 triggers, the Electronic Control Module (ECM) has detected voltage readings outside the acceptable range (typically 0.5-4.5V) from the secondary steering pressure sensor. This fault compromises the machine's ability to maintain safe steering redundancy, which is essential for operator safety and compliance with equipment standards, particularly on used machines where sensor degradation is common.

Common Symptoms

• Steering malfunction warning light illuminated on the instrument cluster
• Reduced steering responsiveness or increased steering effort required
• Intermittent steering assist failure, especially during cold starts on older machines
• ECM derate mode activation limiting machine speed or hydraulic functions
• Audible alarm or continuous beeping when steering is engaged

Potential Causes

The most common technical causes for EID1718 on used Caterpillar excavators include:

• Failed secondary steering pressure sensor due to internal component wear or contamination
• Damaged wiring harness at known rub points near the steering column or chassis frame
• Corroded or loose connector pins at the sensor or ECM interface (common in machines operating in wet/salty environments)
• Hydraulic contamination causing sensor membrane failure or blocked pressure ports
• ECM software corruption or outdated calibration files (rare but possible on older machines)
• Intermittent short to ground in the signal wire, often caused by harness chafing

How to Troubleshoot and Fix Code EID1718

Step 1: Connect Diagnostic Software Use Caterpillar Electronic Technician (Cat ET) software to verify the active fault code and check real-time sensor voltage. Normal operating voltage should read between 0.5-4.5V. A reading of 0V indicates a short to ground, while 5V+ suggests an open circuit or sensor failure.

Step 2: Inspect Wiring Harness and Connectors Physically inspect the secondary steering pressure sensor harness from the sensor to the ECM. On used excavators, pay special attention to areas where the harness contacts the frame, steering column, or hydraulic lines. Look for wire insulation damage, corrosion on connector pins, or moisture intrusion. Clean connectors with electrical contact cleaner and apply dielectric grease.

Step 3: Test Sensor Resistance and Voltage Disconnect the sensor connector and use a digital multimeter to measure resistance across the sensor terminals (typically 200-1000 ohms when functional). Check for voltage supply from the ECM (should be 5V reference voltage). If voltage is present but sensor resistance is out of spec, replace the sensor.

Step 4: Check Hydraulic Pressure and Contamination Verify actual hydraulic pressure in the secondary steering circuit matches sensor readings. Contaminated hydraulic fluid can damage the sensor diaphragm. Sample and test hydraulic fluid for metal particles or water contamination.

Step 5: Clear Code and Road Test After repairs, clear the fault code using Cat ET and perform a thorough operational test under various steering loads. Monitor for code recurrence.

Disclaimer: This guide provides general diagnostic information. Always consult the official Caterpillar service manual for your specific model and serial number. Complex electrical or hydraulic repairs should be performed by certified Caterpillar technicians to ensure safety and warranty compliance.