Case IH P22 – Electronic Engine Control Unit (EECU / ECU): Boost Air Temperature Sensor, Grounded Or Current Above Normal Range

The control module is detecting a voltage signal that is too low (pulled to ground) or a current draw that exceeds the maximum threshold. This typically indicates that the sensor has failed internally (shorted), or the signal wire in the harness is chafed and touching a bare metal ground on the engine block or chassis.

• MXM
• Case IH MXM Series (MXM 120, 130, 140, 155, 175, 190)

1. 1

   Verify the code on the EIC display to confirm if it is T22 (Grounded) or T23 (Open Circuit).

2. 2

   Perform a sensor disconnect test: unplug the Boost Air Temperature Sensor. If the active fault code changes from T22 to T23, the wiring harness is intact and the sensor itself is internally shorted. If the code remains T22, the wiring harness is shorted to ground.

3. 3

   Using a multimeter, measure the resistance across the sensor's pins. Expected values: 595 ohms at 60°C (140°F), 322 ohms at 80°C (176°F), 186 ohms at 100°C (212°F), 112 ohms at 120°C (248°F). If the sensor reads near 0 ohms (continuity), it is shorted.

1. 1

   Power Down

   Turn off the ignition key and disconnect the battery to prevent ECU damage during electrical repairs.

2. 2

   Locate the Sensor

   Find the Boost Air Temperature Sensor (B123) located on the intake manifold / aftercooler piping, before the EGR assembly.

3. 3

   Inspect the Harness

   Disconnect the sensor. Carefully inspect the wiring harness leading back to the ECU. Look for melted insulation, chafing against engine brackets, or moisture intrusion in the connector.

4. 4

   Repair Wiring

   If a short to ground is found in the harness, splice and repair the damaged wire using heat-shrink connectors, then re-loom the harness to protect it from future chafing.

5. 5

   Replace the Sensor

   If the harness tests good but the sensor failed the resistance test, unthread the old sensor from the intake piping and install the new one.

6. 6

   Clear Codes

   Reconnect the battery, turn the key switch to the "ON" position, and verify that the T22 code has cleared from the EIC display.