Case IH 153 – Engine Control Module (ECM): Intake Manifold Temperature Sensor voltage is too high

The Engine Control Module (ECM) supplies a 5-volt reference signal to the intake manifold temperature sensor. If the circuit is open or shorted to a high voltage source, the ECM detects a voltage that is out of range (too high) and logs this fault. Effects include white smoke, the cooling fan staying ON continuously, and reduced engine torque.

• MX Magnum
• STX Steiger
• MX Magnum Series (MX255, MX285)
• Steiger / STX Series (STX 280, STX 440, Steiger 450, 500, 550)
• TG Series
• Floaters (FLX4510)

1. 1

   Visually inspect the intake manifold temperature sensor and engine harness connector for bent, broken, pushed back pins, corrosion, or moisture.

2. 2

   Check for shorts to ground by turning the key OFF, disconnecting the harness, and measuring resistance from pin A of the sensor to the engine block ground (less than 100k ohms indicates an internal short).

3. 3

   Disconnect the engine harness from the ECM, inspect the ECM connector pins for damage, and check the signal circuit in the harness for an open circuit or a short to a voltage source.

1. 1

   Turn the key switch to the OFF position.

2. 2

   Disconnect the electrical plug for the intake manifold temperature sensor.

   Depending on the tractor model, you may need to remove harness retainers or fan shields to access the sensor.

3. 3

   Remove the old sensor from the intake manifold.

   Perform this if the diagnostic checks reveal a faulty sensor (e.g., it fails the resistance check).

4. 4

   Install the new intake manifold temperature sensor and torque it to OEM specifications.

5. 5

   Reconnect the engine harness to the sensor.

   Ensure the connector clicks into place and is free of moisture.

6. 6

   Clear the Fault Code.

   Start the engine and let it idle for 1 minute. The fault code status should change to INACTIVE on your electronic service tool, and the amber CHECK ENGINE lamp will turn off.