New Holland ENG 1800 – Engine Control Module (ECM) / ISM-IDI ENGINE: Diesel Oxidation Catalyst (DOC) IN Temperature Sensor: Out of Voltage - Low

The Exhaust Gas Temperature Sensor (EGTS) located at the inlet of the DOC detects the exhaust gas temperature and converts it into a voltage signal for the engine computer. An "Out of Voltage - Low" condition means the voltage signal returning to the controller has dropped below the minimum acceptable threshold. This typically indicates a short to ground in the sensor's wiring harness, a damaged connector, or an internal short/failure of the sensor itself (which is a PTC-type thermistor).

• L215
• L220
• L223
• L225
• L230
• SR175
• C238
• B90B
• B100B
• TC5050
• TC5060
• TC5070

1. 1

   Visually inspect the DOC IN temperature sensor wiring harness for melted insulation, chafing against the exhaust, or pinched wires that could cause a short to ground.

2. 2

   Disconnect the 2-pin rectangular connector and check for moisture, soot intrusion, or corroded terminals.

3. 3

   Turn the key ON (engine off) and check for the proper 5V reference voltage from the ECU at the harness connector.

4. 4

   Measure the resistance across the two pins of the sensor; if it reads near zero ohms (continuity), the PTC sensor is internally shorted and must be replaced.

1. 1

   Cool Down

   Ensure the engine and exhaust system have completely cooled down to prevent severe burns.

2. 2

   Locate the Sensor

   Find the DOC IN temperature sensor. It is threaded directly into the exhaust piping just before the DOC assembly.

3. 3

   Disconnect Wiring

   Undo any heat-resistant sleeves or snap buttons protecting the wiring, and disconnect the 2-pin female electrical connector.

4. 4

   Remove the Sensor

   Using an appropriately sized wrench or sensor socket, carefully unscrew the threaded sensor from the exhaust pipe. Note: If the sensor is seized, penetrating oil and careful back-and-forth working may be required to avoid stripping the exhaust bung threads.

5. 5

   Install the New Sensor

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (if it does not come pre-applied). Thread it in by hand to prevent cross-threading, then tighten to the OEM torque specification.

6. 6

   Reconnect

   Plug the 2-pin connector back into the engine harness and secure any heat shielding.

7. 7

   Clear Codes

   Use a diagnostic scan tool to clear the ENG 1800 fault code from the Engine ECU, then run the machine to verify the sensor reaches the minimum operating temperature (approx. 140°C for the DOC) without triggering a code.