Case IH 19620 – Engine Control Module (ECM) / EDC: Failure path for P4 Plausibility Check

The Engine Control Module runs a plausibility check to ensure the P4 sensor (Boost Pressure or Intake Manifold Pressure sensor) is reading accurately by comparing it against other pressure sensors (such as ambient/barometric or P3) during Key-ON/Engine-OFF. If the reading is physically impossible or deviates too far from ambient pressure before the engine runs, the ECM flags it as implausible.

• Tier 4b
• Puma
• Magnum
• Optum
• Steiger
• T7
• T8
• T9

1. 1

   Perform a Key-ON / Engine-OFF test using the CNH Electronic Service Tool (EST) to compare the P4 (Boost/Intake) pressure reading to the Ambient (Barometric) pressure reading. They should be nearly identical.

2. 2

   Inspect the wiring harness leading to the P4 pressure sensor for chafed wires, melted insulation from engine heat, or a loose connector.

3. 3

   Check for accompanying turbo/boost codes (such as 19621, 19625, 19626, or 19627) that often accompany P4/P3 issues.

4. 4

   Remove the sensor and check if the sensor tip or the port on the intake manifold is clogged with soot or carbon buildup.

1. 1

   Power Down

   Turn off the engine, remove the key, and turn the battery disconnect switch to the OFF position to prevent electrical shorts.

2. 2

   Locate the Sensor

   Locate the P4 pressure sensor on the engine (typically mounted on the intake manifold or the charge-air piping coming from the turbocharger).

3. 3

   Inspect and Clean

   Disconnect the electrical pigtail. Inspect the pins inside the connector for corrosion or pushed-out terminals. Clean with electrical contact cleaner.

4. 4

   Clear Blockages

   Unbolt the sensor from its mount. Inspect the bore hole. If carbon buildup is present, carefully clean the port so the sensor can accurately read manifold pressure.

5. 5

   Replace the Sensor

   If the wiring is sound and the port is clear, but the sensor still fails the plausibility check on the diagnostic tool, the internal diaphragm of the sensor has failed. Install a new P4 pressure sensor.

6. 6

   Clear and Verify

   Reconnect the battery, turn the key ON, and use the CNH EST to clear the 19620 fault code. Start the engine and verify that the code does not return and that the machine builds boost normally under load.