New Holland 3914 – Engine Control Unit (ECU) / EDC (Electronic Diesel Control): Oxicat Temp Monitoring: Passive monitoring of the oxidation catalyst

This code indicates an anomaly detected during the passive temperature monitoring of the Diesel Oxidation Catalyst (DOC). The controller expects the exhaust temperatures to rise and fall within a specific, modeled range to ensure the DOC is functioning correctly. When the sensor readings drift outside of this expected range, or if the sensor circuit fails, code 3914 is triggered.

• T4 series
• T6 series
• T7 series
• T8 series
• T9 series
• L213
• L216
• L218
• L221
• L228
• L230
• L234
• W-Series loaders (W50TC - W80TC)
• LM series telehandlers
• TH series telehandlers

1. 1

   Inspect the wiring harness and connectors for the DOC inlet and outlet temperature sensors for melted wires, chafing, corrosion, or loose connector pins.

2. 2

   Connect the CNH E.A.SY. diagnostic tool (or equivalent) and monitor live data for the DOC temperature sensors. Look for erratic readings, drop-outs, or a sensor stuck at a default value.

3. 3

   Disconnect the sensor and use a multimeter to measure its resistance. Compare the reading against OEM specifications for the ambient temperature to check for an open or short circuit.

4. 4

   Inspect the exhaust piping upstream of the DOC for leaks, which can cause exhaust gases to bypass the sensor and result in lower-than-expected temperature readings.

1. 1

   Safety First

   Turn off the engine and allow the exhaust system and DOC canister to cool completely. Exhaust components operate at extreme temperatures and pose a severe burn risk.

2. 2

   Locate the Sensor

   Identify the faulty sensor (DOC Inlet or DOC Outlet) on the exhaust aftertreatment assembly.

3. 3

   Disconnect Wiring

   Unplug the electrical connector of the sensor from the main engine wiring harness.

4. 4

   Remove the Sensor

   Using a specialized sensor socket or a flare-nut wrench, carefully loosen and remove the temperature sensor from the exhaust housing. Note: If the sensor is seized due to heat cycling, apply penetrating oil and allow it to soak before applying force to avoid stripping the threads in the DOC housing.

5. 5

   Prepare 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). Do not get any anti-seize on the sensor probe tip, as this will contaminate it.

6. 6

   Install the Sensor

   Thread the new sensor in by hand to prevent cross-threading, then tighten it to the OEM torque specification.

7. 7

   Reconnect

   Plug the electrical connector back into the harness, ensuring the locking tab clicks into place. Route the wire away from direct heat sources.

8. 8

   Clear Codes and Test

   Connect your diagnostic tool, clear the 3914 fault code, and run the engine. Perform a stationary test run or a forced regeneration to verify the sensor is reading correctly and the code does not return.