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

The Engine Control Unit (ECU) is receiving a signal from the ambient (barometric) pressure sensor that is within normal electrical limits, but the pressure value being reported is implausibly high for the current atmospheric conditions.

• MXM
• MXM Series Tractors
• AFX8010 Combines
• 8800 Series Sugar Cane Harvesters
• Steiger Series Tractors
• 580 Super N Backhoes

1. 1

   Consult the service manual to determine if the ambient pressure sensor is an external component or built internally into the Engine ECU

2. 2

   Use a diagnostic tool to read the live atmospheric pressure sensor signal and compare the ECU reading to the actual local barometric pressure

3. 3

   If the sensor is external, inspect the wiring harness between the sensor and the ECU for chafing, moisture in the connector, or slight shorts to voltage

4. 4

   Verify that the 5V reference and ground circuits to the sensor are within specification

5. 5

   If the sensor is internal, perform an ECU swap test with a known-good replacement ECU to see if the fault clears

1. 1

   Prepare machine

   Turn off the machine, remove the key, and disconnect the battery.

2. 2

   Locate sensor

   Locate the ambient pressure sensor on the engine harness.

3. 3

   Disconnect connector

   Disconnect the wiring harness connector (slide the lock to the right, press the release tab, and pull the connector out).

4. 4

   Inspect pins

   Inspect the connector pins for corrosion or damage. Clean with contact cleaner if necessary.

5. 5

   Remove faulty sensor

   Remove the mounting hardware and remove the faulty sensor.

6. 6

   Install new sensor

   Install the new OEM ambient pressure sensor and secure the hardware.

7. 7

   Reconnect harness

   Reconnect the wiring harness, ensuring the locking tab clicks into place.

8. 8

   Clear fault codes

   Reconnect the battery and clear the fault codes using a diagnostic tool or the tractor's H-Menu calibration sequence.

9. 9

   Replace ECU (if internal)

   If diagnostics confirm the internal ECU ambient pressure sensor has failed, replace the Engine ECU. Note: replacing the ECU is not necessary if never running in high altitude.