Case IH PF – Engine Control Unit (ECU) / Engine Electronic Control Module (EEM): Ambient Pressure Sensor (PHY), Shorted To High Source

The signal voltage from the ambient (barometric) pressure sensor is above the normal operational range, indicating a short circuit to a power source, an open circuit on the sensor's ground path, or an internal failure of the sensor itself.

• MXM
• MXM Series (MXM 120, 130, 140, 155, 175, 190)
• CVX Series (140, 150, 160, 175, 195)
• Magnum
• Steiger
• Axial-Flow series (AFX8010, 7230, 8230, 9230, 140 series, 240 series)

1. 1

   Connect the Case IH Electronic Service Tool (EST) to read active and stored fault codes, and monitor the live voltage data for the ambient pressure sensor.

2. 2

   Consult the specific machine's service manual to determine if the ambient pressure sensor is external or internal to the ECU.

3. 3

   If external: Inspect the sensor connector and wiring harness for corrosion, moisture, bent pins, or rubbed wires that could cause a short to a power source.

4. 4

   If internal: Save the error log, erase the codes, and restart the ECU. Run the machine through a driving cycle to see if the fault returns.

1. 1

   Initial Reset

   Clear the error log using the EST and restart the engine. If the fault does not return, it may have been a transient voltage anomaly.

2. 2

   External Sensor Repair

   If the fault remains active and the machine uses an external sensor, disconnect the sensor. Measure the voltage at the signal wire. If it reads high (e.g., 5V or 12V) with the sensor unplugged, there is a short to power in the harness. Repair or replace the wiring harness. If the wiring tests good, replace the external ambient pressure sensor.

3. 3

   Internal Sensor Repair (EEM3/EEM4)

   If the machine uses an ECU with an internal ambient pressure sensor and the fault remains active, the ECU's internal monitoring system has failed. Test the system by plugging in a known-good replacement EEM controller. If the system is functional and the fault is no longer active with the test ECU, the original Engine ECU is defective and must be replaced.