Case IH 1802 – ISM-IDI Engine Controller: DPF Exhaust Temperature Sensor Out Of Range Low

The sensor measuring the exhaust gas temperature at the outlet (post-DPF) of the Diesel Particulate Filter is reporting a voltage that has dropped below the minimum acceptable threshold. This typically indicates an open circuit, a short to ground in the wiring harness, or a completely failed sensor element.

• skid steer
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• SR175
• SV250
• TR320
• Magnum
• Steiger
• Puma
• Farmall

1. 1

   Visually inspect the wiring harness leading to the post-DPF temperature sensor for melted wires, chafing against the hot exhaust, or physical damage from debris.

2. 2

   Disconnect the sensor and inspect the connector pins for corrosion, moisture, or pushed-out terminals.

3. 3

   Use a multimeter to check for an open circuit or a short to ground in the signal wire between the sensor connector and the Engine ECU.

4. 4

   Measure the resistance across the sensor's pins. If the multimeter reads 'OL' (open loop/infinite resistance) or zero resistance (internal short), the sensor itself has failed.

5. 5

   Check for related shared circuit codes (e.g., 1800 or 1804). If present, diagnose for a shared 5V reference or ground wire failure rather than a bad sensor.

1. 1

   Cool Down

   Ensure the machine has been turned off for several hours. The DPF and exhaust system operate at extreme temperatures and can cause severe burns.

2. 2

   Locate the Sensor

   Locate the DPF assembly. Find the temperature sensor positioned at the outlet (downstream/post-DPF) of the filter housing.

3. 3

   Disconnect

   Unplug the electrical connector from the machine's wiring harness.

4. 4

   Remove the Sensor

   Carefully unscrew the sensor from the exhaust bung. Note: Exhaust sensors are prone to seizing. Apply penetrating oil to the threads and allow it to soak if it feels stuck to avoid stripping the exhaust bung.

5. 5

   Prepare the New Sensor

   Apply a small amount of high-temperature exhaust anti-seize to the threads of the new sensor (if it does not come pre-coated). Do not get any anti-seize on the sensor probe itself.

6. 6

   Install

   Thread the new sensor into the DPF housing and tighten to OEM torque specifications.

7. 7

   Reconnect

   Plug the sensor back into the wiring harness and secure any loose wire with high-temp zip ties to keep it away from the exhaust pipe.

8. 8

   Clear Codes

   Use an Electronic Service Tool (EST) or diagnostic scanner to clear the 1802 fault code from the Engine ECU.

9. 9

   Test Run

   Start the engine and monitor the live DPF temperature data to ensure the new sensor is reading correctly and the code does not return.