What is Caterpillar Fault Code SPN1560?

SPN 1560 indicates a problem with the Aftertreatment #1 Diesel Exhaust Fluid (DEF) Tank Temperature Sensor Circuit. This fault code triggers when the Electronic Control Module (ECM) detects an out-of-range signal, open circuit, or short circuit from the DEF tank temperature sensor.

This sensor monitors the temperature of the diesel exhaust fluid stored in the aftertreatment system tank. The ECM uses this data to manage DEF injection rates and prevent freezing or overheating of the fluid. For Caterpillar excavators equipped with Selective Catalytic Reduction (SCR) systems, accurate DEF temperature readings are critical for maintaining emissions compliance and preventing system derate or shutdown. Failure to address SPN1560 can result in reduced engine power, increased emissions, and potential non-compliance with environmental regulations.

Common Symptoms

• Check Engine Light or amber warning lamp illuminated on the instrument cluster
• Engine derate or reduced power output after a predetermined time period
• DEF system warning messages displayed on the monitor
• Exhaust temperature irregularities or poor regeneration performance
• Inducement warnings stating the machine will experience power loss if not repaired within a specified timeframe

Potential Causes

The most common technical causes of SPN1560 on used Caterpillar excavators include:

• Failed DEF tank temperature sensor due to age, contamination, or internal circuit failure
• Damaged wiring harness or connector corrosion at the sensor connection point (common on machines operating in harsh environments)
• Chafed or pinched wires where the harness routes near the DEF tank mounting bracket
• Poor ground connection or corroded ground terminals affecting sensor signal
• ECM software issues or corrupted calibration files (less common but possible)
• Water intrusion into the connector causing intermittent shorts or opens

How to Troubleshoot and Fix Code SPN1560

Step 1: Visual Inspection Begin by inspecting the DEF tank temperature sensor and its wiring harness for obvious damage. On used excavators, check for wire chafing where the harness contacts the tank frame or mounting brackets. Inspect the connector for corrosion, bent pins, or moisture intrusion—clean with electrical contact cleaner if necessary.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. Compare readings to Caterpillar specifications (typically 2,000-3,000 ohms at room temperature, varying with temperature). Check for continuity in the wiring harness from sensor to ECM connector. Verify voltage supply (typically 5V reference) from the ECM with key on, engine off.

Step 3: Advanced Diagnostics Connect Caterpillar Electronic Technician (Cat ET) diagnostic software to read freeze frame data and monitor live sensor values. Compare actual DEF temperature readings with ambient temperature—significant deviation indicates sensor failure. Check for intermittent faults by wiggling harness connections while monitoring data.

Step 4: Repair and Verification Replace the DEF tank temperature sensor if out of specification or damaged. For used machines, always replace corroded connectors and repair damaged harness sections with proper gauge wire and heat shrink protection. After repairs, clear codes using Cat ET and perform a regeneration cycle to verify proper system operation.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Caterpillar service manual for your specific machine model and consider professional diagnostic assistance for complex electrical issues.