Case IH 3169 (F-4009-06) - ECU – Engine Control Unit (ECU): Fuel filter heater ECU driver has an over temperature error / Fuel Filter Heater Relay - Signal Not Plausible

The ECU has detected an over-temperature condition on the internal driver circuit that controls the low side of the auxiliary power relay for the fuel filter heater. The ECU shuts down the circuit because excessive current draw (usually caused by a short circuit in the relay, the heating element, or the wiring harness) is causing the ECU's internal components to overheat.

• VESTRUM CVX
• Case IH 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Case IH Magnum Series (235, 260, 290, 315, 340, 380)
• Case IH Maxxum Series
• Case IH Optum Series
• Case IH Steiger Series

1. 1

   Inspect the fuel filter heater relay in the chassis fuse block or main relay center for signs of melting, heat discoloration, or a burnt smell.

2. 2

   Test the fuel filter heating element by disconnecting the wiring harness and measuring resistance across the terminals. A reading of zero or near-zero ohms indicates an internal short circuit.

3. 3

   Inspect the wiring harness running from the Engine ECU to the fuel filter heater relay, and from the relay to the heating element, for chafed insulation. Test the low-side control wire for a short to ground or short to power.

4. 4

   Verify the condition of the fuse associated with the fuel heater circuit to ensure it hasn't blown or been replaced with an incorrectly sized (oversized) fuse.

1. 1

   Power down machine

   Turn off the machine, remove the key, and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Replace the relay

   If the relay is faulty or shows signs of thermal stress, remove it from the fuse/relay panel and install a new OEM micro relay.

3. 3

   Replace the heating element

   If the element is shorted: Place a drain pan under the fuel filter assembly, drain the fuel, remove the faulty heating element, and install the new one ensuring the O-ring is properly seated and lubricated with clean diesel fuel.

4. 4

   Repair wiring

   Splice and heat-shrink any damaged or chafed wires found during the diagnostic phase. Secure the harness away from high-heat or high-vibration areas using zip ties.

5. 5

   Reassemble and prime fuel system

   Reconnect the battery. Turn the key to the ON position to allow the electric lift pump to prime the fuel system (or use the manual bleed screw if applicable).

6. 6

   Clear codes

   Access the diagnostic menu on the cab display (e.g., AFS Pro 700) or use a dealer service tool to clear the inactive fault codes. Start the engine and verify the code does not return.