Case IH 3457 – ECU: Intake Manifold Temp Sensor Voltage High

The Engine Control Unit (ECU) detects that the intake manifold temperature sensor signal voltage is greater than 4.93 V for longer than 500 milliseconds, indicating an open circuit or a short to a high-voltage source. Consequently, the ECU defaults to a fixed temperature value of 29.96 °C (85.93 °F) and derates engine power output to protect the system.

• Steiger T4B
• 240 Series Axial-Flow Combines
• 7240
• 8240
• 9240
• 30 Series Combines
• 7230
• 8230
• 9230
• T8 Series
• MX Magnum Series
• MX230
• MX255
• Farmall 40-45-50
• 8800 Series Sugar Cane Harvesters
• FLX4510 Floaters

1. 1

   Visually inspect the intake manifold temperature sensor connector and wiring harness for physical damage, corrosion, or loose pins.

2. 2

   Disconnect the sensor and verify the 5V reference supply and ground are present at the harness connector using a multimeter.

3. 3

   Test the signal wire between the sensor connector and the ECU for continuity, ensuring it is not shorted to a 12V power source or ground.

4. 4

   Ensure the tractor battery power supply has not been improperly connected to an external power supply causing voltage spikes.

1. 1

   Prepare machine

   Turn off the engine, remove the key, and disconnect the battery to prevent electrical shorts.

2. 2

   Access the sensor

   Locate the intake manifold temperature sensor on the engine block/intake piping. Remove fan shields, harness retainers, or loosen the air cleaner outlet tube at the turbocharger elbow if necessary.

3. 3

   Remove faulty sensor

   Disconnect the electrical plug for the intake manifold temperature sensor and unthread the faulty sensor from the intake manifold.

4. 4

   Install new sensor

   Thread the new replacement sensor into the manifold and tighten to OEM torque specifications. Reconnect the electrical plug.

5. 5

   Reassemble components

   Reinstall any shields, retainers, or intake piping that were removed to access the sensor.

6. 6

   Clear codes and reset inducement

   Reconnect the battery and use a diagnostic service tool (such as a PT Box, TEXA, or Cojali tool) to clear the fault codes. Perform an Inducement Unlock / Counter Reset via the diagnostic tool to remove the engine derate.