Case IH 154 – Engine Control Module (ECM): Intake Manifold Temperature Sensor voltage is too low

The ECM detects that the intake manifold temperature sensor signal voltage has dropped below the acceptable minimum threshold, indicating a short circuit to ground in the wiring harness or an internal short within the sensor.

• MX Magnum
• STX Steiger
• Case IH MX Magnum Series (MX230, MX255)
• Case IH Steiger and STX Series (STX 280, Steiger 500, Steiger 550)
• Case IH 8000 and 8800 Series Sugarcane Harvesters

1. 1

   Check for multiple active codes, as the sensor shares return wires in the engine harness with other sensors; troubleshoot shared harness first if multiple codes exist.

2. 2

   Inspect the intake manifold temperature sensor connector and the ECM harness connector for moisture, corrosion, or pushed-back pins.

3. 3

   Test the signal circuit in the engine harness with a multimeter to check for a short to ground.

4. 4

   Test the sensor itself to see if the signal circuit is shorted to the return/ground internally (internal short).

1. 1

   Turn the ignition keyswitch to the OFF position.

2. 2

   Locate the intake manifold temperature sensor.

   It is typically located on the side of the air intake manifold near the middle of the cylinder head. On some models like the MX series, you may need to remove the left/right fan shields or harness retainers to access it.

3. 3

   Disconnect the electrical plug for the intake manifold temperature sensor.

4. 4

   Repair or replace the affected section of the harness.

   Perform this step if your diagnostic tests revealed a short in the wiring harness.

5. 5

   Remove the old sensor and install a replacement.

   Perform this step if the wiring is intact but the sensor failed the resistance test (internally shorted).

6. 6

   Reconnect the electrical plug to the sensor.

7. 7

   Validate the Repair.

   To clear the fault code, perform a key cycle, start the engine, and let it idle for at least 1 minute. The fault code status should change to INACTIVE, and the ECM will turn off the amber CHECK ENGINE lamp.