Case IH 221 – Engine Controller (ENG / ECM): Ambient Air Pressure Sensor Voltage is too high

In electronic engine control systems, a "voltage too high" condition typically points to an open circuit (a broken wire or disconnected plug), a short to a power source in the sensor's wiring harness, or an internally failed sensor.

• MX Magnum
• STX Steiger
• Case IH MX Magnum Tractors
• Case IH TG Series Tractors
• Case IH Steiger Tractors
• Case IH Puma Tractors

1. 1

   Inspect the ambient air pressure sensor connector for loose, bent, or corroded pins.

2. 2

   Check the sensor cabling/wiring harness for visible damage, wire breaks (open circuits), or chafing that could cause a short circuit to a voltage source.

3. 3

   Use a multimeter to verify the reference voltage and ground at the sensor connector to rule out ECM or main harness issues.

1. 1

   Locate sensor

   Locate the Ambient Air Pressure Sensor on the engine.

2. 2

   Inspect connector

   Disconnect the sensor's electrical connector and inspect it.

3. 3

   Repair wiring

   If wiring damage is found during the diagnostic checks, repair the broken wire or short circuit in the harness.

4. 4

   Remove faulty sensor

   If the wiring and connector test good, the sensor itself has likely failed internally. Remove the mounting hardware and remove the faulty sensor.

5. 5

   Install new sensor

   Install the new Ambient Air Pressure Sensor and plug in the connector.

6. 6

   Clear fault codes

   Turn the key on and use a diagnostic tool to clear the fault codes from the Engine Controller.

7. 7

   Verify repair

   Start the machine and verify that Fault Code 221 does not return.