Case IH 222 – Engine Control Module (ECM): Ambient Air Pressure Sensor Circuit - Voltage Below Normal, or Shorted to Low Source

The Engine Control Module (ECM) has detected a low signal voltage on the ambient air (barometric) pressure sensor circuit (often below 39 mV). The ECM will default to a preset barometric pressure value, illuminate the amber Check Engine light, and typically enforce an engine power derate (often around 15%).

• MX Magnum
• STX Steiger
• Steiger tractors
• Steiger 425
• Magnum tractors
• Axial-Flow combines

1. 1

   Check for Multiple Faults: Check if other sensor codes are active, which would point to a shared harness short or ECM issue rather than a failed pressure sensor.

2. 2

   Visual Inspection: Inspect the engine harness and the sensor connector for moisture, dirt, pushed-back pins, expanded pins, or a broken connector shell.

3. 3

   Wiring Integrity: Check the wire insulation for damage, rubbing, or shorts to ground.

4. 4

   Voltage Check: Verify that the ECM is providing a 5-volt supply to the sensor on the supply circuit and that the ground return circuit is intact.

5. 5

   Data Monitor: Use an electronic service tool to compare the actual atmospheric pressure with the reported air pressure reading. If the reading is erratic or stuck at a default value, the sensor or its wiring is compromised.

1. 1

   Turn the keyswitch to the OFF position and ensure the engine is not running.

2. 2

   Locate the ambient air pressure sensor.

   On ISB/QSB engines, it is often a combination temperature/pressure sensor located in the OEM intake air plumbing. On ISC/ISL/QSM11 engines, it is usually mounted on the main engine harness near the ECM or intake manifold.

3. 3

   Disconnect the sensor from the engine harness.

4. 4

   Inspect the connector pins on both the sensor and the harness for corrosion or damage.

   Clean if necessary.

5. 5

   Disconnect the engine harness from the ECM and check the sensor supply voltage and circuit response using a multimeter.

6. 6

   If the wiring harness fails the continuity or short-to-ground tests, locate the damaged section and repair or replace the wiring harness.

7. 7

   If the wiring harness and ECM 5V supply are good, but Fault Code 222 remains active, the sensor has failed internally.

   Replace the ambient air pressure sensor.

8. 8

   To validate the repair: Reconnect all harnesses, perform a key cycle, start the engine, and let it idle for 1 minute.

   The fault code status on the service tool should change to INACTIVE, and the amber Check Engine lamp will turn off. Clear the inactive faults from the ECM memory.