Case IH 19674 – Engine Control Module (ECM): Turbine downstream pressure sensor comparison to modeled pressure failure.

The Engine Control Unit calculates an expected (modeled) exhaust gas pressure downstream of the turbocharger based on current engine load, speed, and airflow. This fault triggers when the physical pressure measured by the Turbine Downstream Pressure Sensor (often referred to as Exhaust Gas Pressure Sensor P3) drifts significantly from this expected mathematical model.

• Tier 4b
• Puma
• Optum
• Magnum
• Maxxum
• Steiger
• N-Series backhoes (580N, 590SN)
• G-Series wheel loaders (1021G, 1121G)
• Farmlift telehandlers

1. 1

   Perform a Key-On, Engine-Off (KOEO) test using a diagnostic tool to verify the sensor reads atmospheric pressure; if it reads significantly higher or lower, the sensor has internally drifted (sensor failure cause).

2. 2

   Inspect the metal signal tube connecting the sensor to the exhaust stream for heavy soot, carbon buildup, or moisture freezing (clogged tube cause).

3. 3

   Check for physical exhaust leaks at the V-band clamps, gaskets, and flex pipes between the turbocharger outlet and the DOC/DPF inlet (exhaust leak cause).

4. 4

   Inspect the sensor's pigtail and main engine harness for chafing, melted wires, or corrosion, and verify the 5V reference supply and ground.

1. 1

   Preparation

   Turn off the battery disconnect switch. Allow the engine and the Clean Emissions Module (CEM) exhaust components to cool completely.

2. 2

   Locate the Sensor

   Locate the Turbine Downstream Pressure Sensor. On most FPT engines, it is mounted on a bracket near the right side of the engine or directly on the Clean Emissions Module, connected to the exhaust pipe via a metal signal tube.

3. 3

   Disconnect Wiring

   Carefully unplug the electrical connector from the sensor.

4. 4

   Remove the Sensor and Tube

   Use a flare nut wrench to loosen the fitting that secures the signal tube to the exhaust pipe. Unbolt the sensor from its mounting bracket.

5. 5

   Clean the Port

   Use a wire pipe cleaner and brake parts cleaner to clear any carbon out of the metal signal tube. If the tube is completely caked with hard carbon and cannot be cleared, it must be replaced.

6. 6

   Install the New Sensor

   Thread the new sensor onto the signal tube and mount it to the bracket. Tighten the fittings to OEM torque specs (do not overtighten the hollow tube fittings as they can crack).

7. 7

   Reconnect

   Plug in the electrical connector.

8. 8

   Clear and Test

   Reconnect the battery, connect your diagnostic tool, clear the 19674 inactive code, and perform a stationary forced DPF regeneration or a loaded test run to verify the physical pressure now matches the modeled pressure.