Case IH 3154 – Engine Control Unit (ECU) / Electronic Diesel Control (EDC): Grid Heater Relay Shorted to Battery Voltage

The Engine Control Unit (ECU) monitors the intake air heater relay control circuit for a 'short to high source' condition. If the expected voltage drop is incorrect or a short to battery voltage is detected in the wiring or inside the relay itself, this fault is logged.

• Steiger T4B
• Magnum 235
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• Magnum 290
• Magnum 315
• Magnum 340 Series 4
• Maxxum 110
• Puma 175
• Puma 185 CVT
• Steiger
• 7240 Combine
• 8240 Combine
• 9240 Combine
• Patriot 3230
• Case 580 Super N
• Case 580SN WT
• Case 590SN
• Case 621G Loader

1. 1

   Inspect the wiring harness between the ECU and the grid heater relay for any chafing, melting, or exposed copper that could be shorting directly to a 12V/24V battery source.

2. 2

   Test the grid heater relay for an internal short circuit. The fault is often caused by the relay contacts fusing together or an internal short to the power stage.

3. 3

   Check the trigger wires from the ECU to verify that they are not receiving unintended battery voltage when the key is on but the grid heater is commanded off.

1. 1

   Disconnect Power

   Disconnect both negative battery cables at the batteries.

2. 2

   Locate the Relay

   The grid heater relay is typically located in the engine compartment. On FPT/Iveco engines, it is often on the RH side of the engine near the air intake pipe. On Cummins applications, it is usually attached to a bracket near the passenger-side battery tray.

3. 3

   Disconnect Wiring

   Disconnect the small relay trigger wires (note their positions). Then, remove the retaining nuts and disconnect the heavy-gauge power cables from the mounting studs.

4. 4

   Remove the Relay

   Remove the mounting bracket screws and detach the relay assembly from the machine.

5. 5

   Install the New Relay

   Position the new relay and secure the mounting bracket screws.

6. 6

   Reconnect Wiring

   Reattach the heavy-gauge cables to the studs and tighten the nuts. Reconnect the trigger wires to their correct terminals.

7. 7

   Finalize

   Reconnect the negative battery cables. Clear the fault codes via the diagnostic menu or scan tool, and cycle the key to verify the code does not return.