Case IH 3905 (DTC 8814) - ECU – Engine Control Unit (ECU): Intake air heater ECU driver has an over-temperature error

The internal driver circuit inside the ECU that commands the intake air heater relay has overheated. This is almost always caused by excessive current draw, typically resulting from a shorted intake air heater relay, a shorted heater element, or the relay supply wire being shorted to ground.

• MAXXUM T4E
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Puma Series (Puma 185, 200, 230)
• Maxxum Series (115, 125, 130)
• Magnum Series
• A8000 / A8800 Sugar Cane Harvesters
• Patriot Series (3340)

1. 1

   Test the intake air heater relay for an internal short circuit, as a failed relay is the most common cause of excessive current draw on the ECU driver.

2. 2

   Inspect the wiring harness, specifically tracing the relay supply wire and the control wire from the ECU to the relay, looking for chafing, melted insulation, or shorts to the chassis/ground.

3. 3

   Check the grid heater element at the intake manifold for a dead short to ground.

4. 4

   Inspect the high-amp fuse (300A blade fuse) or fusible link protecting the grid heater circuit.

1. 1

   Disconnect Power

   Disconnect the negative battery cable(s) to prevent accidental arcing or further damage to the ECU.

2. 2

   Locate Components

   Locate the intake air heater relay (usually mounted near the engine block or intake manifold) and the grid heater element on the intake manifold.

3. 3

   Remove the Relay

   Disconnect the electrical connections from the relay.

4. 4

   Test/Replace the Relay

   Using a multimeter, test the relay's control circuit for continuity and resistance. If the resistance is out of spec (indicating a short), replace the relay.

5. 5

   Repair Wiring

   If the relay tests fine, repair or replace the section of the wiring harness that is shorting to ground. Ensure all wire straps and retainers are securing the harness away from hot engine components.

6. 6

   Reassemble

   Install the new relay or repaired harness. Reconnect all electrical connections and the battery.

7. 7

   Clear Codes

   Connect a diagnostic tool, clear the fault code, and cycle the key to verify the code does not return during the cold-start grid heater cycle.