Case IH 3993 – Engine Control Module (ECM) / Engine Controller: DPF Intake Temperature Higher Than 800 deg C

This is a critical fault indicating that the exhaust gases entering the Diesel Particulate Filter have reached dangerously high temperatures. This condition is typically caused by either a malfunctioning temperature sensor providing a false high reading, or an actual thermal event in the exhaust system (usually due to excessive unburned fuel entering the exhaust stream and igniting inside the Diesel Oxidation Catalyst/DPF).

• skid steer
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• SR175
• Steiger Tractors
• Maxxum Tractors

1. 1

   Cold Engine Sensor Verification: Connect the Case IH Electronic Service Tool (EST) with the engine off and completely cold. Check if DPF Intake Temperature matches ambient temperature (diagnosing a false high reading).

2. 2

   Wiring Harness Inspection: Inspect the wiring harness between the DPF Intake Temperature Sensor and the Engine Controller for chafing, melting, or a short-to-voltage.

3. 3

   Fuel System Check: If the sensor is reading accurately (diagnosing an actual thermal event), check for leaking fuel injectors or a faulty aftertreatment hydrocarbon doser/burner dumping raw fuel into the exhaust.

4. 4

   Physical Aftertreatment Inspection: Inspect the exterior of the DOC and DPF for heat discoloration. Remove the DPF and inspect the internal substrate for melting, cracking, or face-plugging.

1. 1

   Isolate the Sensor

   If the EST shows an implausible high temperature on a cold engine, disconnect the DPF Intake Temperature Sensor.

2. 2

   Test the Circuit

   If the temperature reading on the EST drops to a default low value when disconnected, the sensor is internally shorted and must be replaced. If the reading remains at 800°C+, there is a short in the wiring harness to the ECM that must be traced and repaired.

3. 3

   Address Fuel Leaks (If Applicable)

   If the sensor is functioning properly and the exhaust actually reached 800°C, diagnose and replace any leaking fuel injectors to prevent raw fuel from continuing to ignite in the exhaust.

4. 4

   Inspect and Replace Damaged Aftertreatment

   Extreme temperatures above 800°C often melt the precious metals inside the DPF. If the substrate is damaged, replace the DPF (and potentially the DOC).

5. 5

   Reassembly and Verification

   Install the new sensor or components. Clear the fault codes using the EST.

6. 6

   Regeneration Test

   Perform a forced stationary DPF regeneration while monitoring the DOC and DPF intake/exhaust temperatures to ensure they remain within normal operating parameters (typically between 400°C and 650°C).