Case IH F-729-05 - ECU – Engine Control Unit (ECU) / Engine Control Module (ECM): Intake air heater actuator has an open load error

The control unit is monitoring the intake air heater relay control circuit and has detected an open circuit condition, a disconnected line, or a lack of electrical load. This prevents the intake air heater from functioning properly, which can lead to degraded engine starting performance in cold temperatures and the emission of white smoke.

• MAGNUM AFS Connect
• Case IH 240 Series Axial-Flow Combines
• Case IH Farmall 40, 45, and 50 Tractors
• Case IH Magnum Tractors (MX210, MX230, MX255, MX285)
• Case IH Puma Tractors

1. 1

   Check that the tractor battery power supply has not been connected to an external power supply. If an external power supply is connected to the tractor, disconnect it and test the system for normal operation.

2. 2

   Inspect the electrical connection on the grid heater stud to ensure it has not been removed, damaged, or disconnected.

3. 3

   Check that the contacts on the connector of the preheating relay sensor and the 'MOTOR' connector of the ECU are not oxidized and that they are firmly secured.

4. 4

   Check that the pre-heating control relay works properly. Ensure it is not 'stuck' in the ON or OFF position.

5. 5

   With the starter key in the 'OFF' position and the ECU connector disconnected, connect a test meter to the pins to check for an open circuit or a short to ground in the relay supply wire.

1. 1

   Secure the Machine

   Park the vehicle on a flat, level surface, set the parking brake, turn the engine off, and chock the wheels to prevent the vehicle from moving.

2. 2

   Disconnect Power

   Disconnect the battery power supply (using the battery disconnect switch if equipped) to prevent electrical shock or short circuits during repair.

3. 3

   Clean Connections

   If the diagnostic phase revealed oxidized contacts on the ECU or relay connectors, clean the pins thoroughly and re-secure the harness.

4. 4

   Replace the Relay

   If the intake air heater relay is confirmed to have an open internal coil or is malfunctioning, unbolt the electrical leads from the relay terminals, unbolt the relay from its mounting bracket, and remove it.

5. 5

   Install New Parts

   Mount the new intake air heater relay. Reconnect the wiring harness and ensure the connections on the grid heater stud are tight.

6. 6

   Test the System

   Reconnect the battery. Turn the starting switch to the ON position and use the machine's diagnostic display or a service tool to verify that the F-729-05 / SPN 729 FMI 5 fault code has cleared and the heater operates normally.