Case IH tE – Engine Control Unit (ECU): Ambient Pressure Sensor (PHY), Data Valid But Above Normal Range

The Engine Control Unit (ECU) is receiving a signal from the ambient (barometric) air pressure sensor that falls within the valid electrical operating range (meaning there is no open or short circuit), but the pressure reading is physically higher than what is considered normal or possible for the current operating conditions.

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190
• Magnum
• Steiger
• Axial-Flow

1. 1

   Determine Sensor Location: Depending on the exact engine model, the ambient pressure sensor is either mounted externally on the engine harness or is internal to the ECU (such as on EEM3 controllers).

2. 2

   External Sensor Check: If the sensor is external, disconnect the sensor connector. Inspect the pins for corrosion, moisture, or pushed-back terminals.

3. 3

   Wiring Check: With a multimeter, verify that the sensor is receiving the correct 5V reference voltage and has a solid ground.

4. 4

   Internal Sensor Check (EEM3 Controllers): OEM troubleshooting for EEM3 controllers states that if the internal ambient pressure sensor fails, you must check the ECU operation by swapping it with a known-good EEM3 controller. If the system is functional and the fault is not active with the replacement ECU, the original ECU is confirmed defective.

5. 5

   Environmental Check: Verify that the machine is not being operated at an extreme, abnormal altitude that could temporarily skew barometric readings.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical spikes.

2. 2

   Access the Sensor/ECU

   Locate the ambient pressure sensor on the engine block/intake piping, or locate the ECU if the sensor is internal.

3. 3

   For External Sensors

   Disconnect the wiring harness from the sensor. Remove the mounting bolt(s) holding the sensor in place and pull the sensor out. Install the new ambient pressure sensor and torque to OEM specifications. Reconnect the wiring harness, ensuring the locking tab clicks into place.

4. 4

   For Internal Sensors (ECU Replacement)

   If diagnostics prove the internal ECU sensor has failed, the ECU cannot be serviced in the field. Disconnect the main wiring harnesses from the ECU. Unbolt and remove the defective ECU. Install the replacement ECU and reconnect the harnesses. (Note: A new ECU will require dealer programming/calibration to match the tractor).

5. 5

   Clear Codes

   Reconnect the battery, turn the key to the ON position, and use a diagnostic tool (or the tractor's H-Menu) to clear the inactive fault codes. Start the engine and verify the code does not return.