What is Caterpillar Fault Code SPN 2370?

SPN 2370 indicates a malfunction in the Diesel Exhaust Fluid (DEF) Tank Temperature Sensor Circuit (Data Erratic, Intermittent, or Incorrect). This fault code triggers when the Electronic Control Module (ECM) detects inconsistent, out-of-range, or unreliable temperature readings from the DEF tank temperature sensor, which is part of the Selective Catalytic Reduction (SCR) aftertreatment system.

This code is critical for Caterpillar excavators equipped with Tier 4 Final emissions systems. The DEF tank temperature sensor provides essential data to the ECM for proper SCR operation, ensuring optimal DEF injection rates and preventing crystallization in cold conditions. When SPN 2370 is active, the machine may enter derate mode to protect emissions compliance, directly impacting productivity on the jobsite.

Common Symptoms

• Check Engine Light or Malfunction Indicator Lamp (MIL) illuminated on the dashboard
• Engine derate or reduced power output after a set period (typically after a countdown timer expires)
• SCR system warnings displayed on the operator monitor indicating DEF system faults
• Difficulty starting in cold weather conditions due to improper DEF heating management
• Intermittent fault logging that appears and disappears during operation cycles

Potential Causes

The most common technical causes for SPN 2370 on used Caterpillar excavators include:

• Corroded or damaged wiring harness connections at the DEF tank temperature sensor (common wear point due to environmental exposure)
• Failed DEF tank temperature sensor itself, often due to crystallized DEF contamination or internal component degradation
• Chafed or pinched wiring along the harness routing from the DEF tank to the ECM (check mounting brackets and harness supports)
• Poor ground connections causing erratic voltage signals to the ECM
• Contaminated DEF fluid causing sensor fouling or incorrect readings
• ECM software calibration issues requiring updates (less common but possible on older machines)

How to Troubleshoot and Fix Code SPN 2370

Step 1: Visual Inspection of Wiring and Connections Begin by thoroughly inspecting the DEF tank temperature sensor harness from the sensor to the ECM. On used excavators, pay special attention to areas where the harness contacts the frame, passes through grommets, or is exposed to road debris and moisture. Look for chafing, cracked insulation, corrosion on connector pins, or bent terminals.

Step 2: Test the DEF Tank Temperature Sensor Disconnect the sensor connector and use a digital multimeter to measure resistance across the sensor terminals. Compare readings against Caterpillar specifications (typically 2,000-3,000 ohms at room temperature, but verify with service manual). Also check for voltage supply at the harness connector (should be approximately 5 volts reference voltage from the ECM).

Step 3: Check for Intermittent Faults and Sensor Contamination Remove the sensor from the DEF tank and inspect for crystallized DEF buildup or physical damage. Clean the sensor carefully with distilled water if contamination is present. Use Caterpillar Electronic Technician (Cat ET) diagnostic software to monitor live sensor data and check for erratic readings during wiggle testing of connectors and harnesses.

Step 4: Verify Ground Circuits and ECM Connections Test the ground circuit continuity from the sensor to chassis ground and from the ECM ground points. Resistance should be less than 5 ohms. For used machines, clean all ground connection points and apply dielectric grease to prevent future corrosion.

Step 5: Replace Components as Needed If testing confirms sensor failure, replace with a genuine Caterpillar DEF tank temperature sensor. If wiring damage is found, repair using proper gauge wire and weatherproof connectors, or replace the affected harness section. After repairs, clear codes with Cat ET and perform a system test cycle.

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Disclaimer: This guide provides general troubleshooting information for SPN 2370 on Caterpillar excavators. Always consult the specific service manual for your machine model and serial number. For complex electrical diagnostics or emissions system repairs, professional consultation with a certified Caterpillar technician is recommended to ensure proper repair and compliance with emissions regulations.