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

The Ambient (Atmospheric) Pressure Sensor is sending a signal that is recognized as valid data, but the value falls below the normal expected operating range. This typically means the sensor has failed internally and is reading an artificially low atmospheric pressure, though it can occasionally be triggered if the machine is operating at an extreme altitude.

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190
• Maxxum Series
• AFX8010 Combines

1. 1

   Verify operating conditions to ensure the machine is not actually operating at an extreme altitude that would legitimately drop the atmospheric pressure below the minimum threshold.

2. 2

   Check for accompanying codes (e.g., FL1 5Vdc Supply defect). If the 5V reference circuit is failing, it will cause the pressure sensor to read low.

3. 3

   Perform an ECU swap test with a known-good EEM3 controller/ECU to determine if the internal ambient pressure sensor is defective.

1. 1

   Confirm sensor failure

   For Internal ECU Sensor: Confirm the sensor failure via the ECU swap test.

2. 2

   Replace ECU

   For Internal ECU Sensor: Replace the Engine Control Unit (ECU). Note: Case IH service documentation explicitly notes that replacing the ECU is 'not necessary if never running in high altitude.'

3. 3

   Locate sensor

   For External Sensor: Locate the Barometric/Ambient Pressure Sensor on the engine harness.

4. 4

   Inspect connector

   For External Sensor: Disconnect the sensor and inspect the connector pins for corrosion or pushed-out pins.

5. 5

   Verify voltage and ground

   For External Sensor: Use a multimeter to verify that the sensor is receiving a 5V reference signal and a good ground from the ECU.

6. 6

   Replace sensor

   For External Sensor: If voltage and ground are correct, the sensor itself has failed and must be replaced.