Case IH 3914 – Engine Control Module (ECM): Oxicat Temp Monitoring: Passive monitoring of the oxidation catalyst

The Engine Control Module has detected an implausible temperature reading or an unexpected temperature differential between the exhaust gas temperature sensors located upstream and downstream of the Diesel Oxidation Catalyst (DOC).

• FPT Tier 3 engines
• FPT Tier 4a engines
• FPT Tier 4B engines
• NEF 4.5L engines
• NEF 6.7L engines
• Cursor engines
• Puma series

1. 1

   Monitor live data for upstream and downstream DOC temperature sensors during a cold start using a diagnostic tool to check for stuck, out-of-range, or erratic readings.

2. 2

   Inspect the physical mounting of the upstream and downstream DOC temperature sensors to ensure they are not loose, incorrectly mounted, or swapped.

3. 3

   Inspect wiring harnesses and connectors for the DOC temperature sensors for chafing, corrosion, or short circuits to ground or battery.

4. 4

   Verify if the machine was exposed to extreme ambient temperature changes (e.g., block heater usage or direct sunlight after freezing) which can cause temporary ghost failures.

5. 5

   Check for any exhaust leaks before or around the DOC that could cause abnormal temperature readings.

1. 1

   Connect the diagnostic tool and read the live exhaust temperature sensor data to identify which sensor (upstream or downstream of the DOC) is reporting the implausible value.

   Identify faulty sensor

2. 2

   Turn off the engine and allow the exhaust system to cool completely to avoid severe burns.

   Cool exhaust system

3. 3

   Locate the faulty DOC temperature sensor on the exhaust aftertreatment assembly.

   Locate sensor

4. 4

   Disconnect the sensor's electrical connector. Use a multimeter to check the resistance of the sensor and verify the continuity of the wiring harness back to the ECM.

   Check resistance and continuity

5. 5

   If the wiring is intact but the sensor fails the resistance check (or was reading implausibly on the diagnostic tool), remove the sensor using the appropriate wrench.

   Remove faulty sensor

6. 6

   Apply a small amount of high-temp anti-seize compound to the threads of the new sensor (if not pre-applied by the manufacturer) and install it into the exhaust pipe. Torque to the manufacturer's specification.

   Install new sensor

7. 7

   Reconnect the electrical connector and ensure the wiring is secured away from extreme heat sources and moving parts.

   Reconnect and secure wiring

8. 8

   Clear the fault codes using the diagnostic tool.

   Clear fault codes

9. 9

   Perform a test run, bringing the engine up to operating temperature under load, to verify the DOC temperatures are reading correctly and the fault code does not return.

   Perform test run