New Holland 1800 – ENGINE: DOC Inlet Temp Sensor Voltage Low

The Engine Control Module (ECM) has detected an abnormally low voltage signal from the Diesel Oxidation Catalyst (DOC) inlet temperature sensor. This indicates a potential issue with the sensor's power supply, circuit, or the sensor itself. An incorrect low reading impairs the ECM's ability to monitor after-treatment efficiency and control regeneration cycles, which can lead to engine power derate.

• T4 Series
• T5 Series
• T6 Series
• T7 Series
• T8 Series
• T9 Series
• CR Series
• CX Series
• FR Series
• Skid Steer Loaders
• Compact Track Loaders

1. 1

   Visually inspect the wiring harness leading to the DOC inlet temperature sensor for chafing, melting, or breaks.

2. 2

   Examine the sensor's electrical connector for corrosion, bent or spread pins, and ensure it is securely latched.

3. 3

   With Key OFF, disconnect the sensor and check for a short to ground by measuring resistance between the signal wire pin and chassis ground (should be an open circuit).

4. 4

   Disconnect the ECM connector and check for continuity on the signal wire between the sensor connector and the ECM to rule out an open circuit.

5. 5

   Measure resistance across the two pins of the sensor itself to check for an internal short or open circuit.

1. 1

   Prepare machine for service

   Turn the ignition to the OFF position and disconnect the vehicle's batteries before beginning any repair work.

2. 2

   Repair wiring or connectors

   If diagnostic checks reveal a short to ground, open circuit, or damaged connector, repair or replace the affected section of the harness. Ensure all connections are clean and secure.

3. 3

   Replace DOC inlet temperature sensor

   If the sensor fails the resistance test, locate it on the exhaust piping just before the DOC. Disconnect the electrical connector, unscrew the old sensor, and install the new one tightened to the manufacturer's specified torque.

4. 4

   Clear codes and verify repair

   Reconnect the batteries, turn the ignition ON, and use a diagnostic tool to clear the active fault code. Start the engine and verify the code does not return.