Case IH 3698 – Engine Control Unit (ECU) / Electronic Diesel Control (EDC): Glow Plugs: Array of DFCs for Failure in Cylinder 4 Glow Plug

The engine control system has detected an electrical fault, open load, or short circuit specifically on the glow plug heating circuit for Cylinder 4.

• Case IH Farmall series tractors
• Case skid steer loaders (SR175)
• Case compact track loaders
• Equipment with F5C and F5H diesel engines

1. 1

   Inspect the wiring harness and electrical connector leading to the Cylinder 4 glow plug for chafed wires, melted insulation, or corroded terminals

2. 2

   Perform a resistance test on the Cylinder 4 glow plug using a multimeter (an infinite reading indicates an open internal circuit/burnt-out plug, while zero indicates a dead short)

3. 3

   Perform a voltage supply test by turning the key to the 'ON' position (pre-heat phase) and verifying that the glow plug control unit is sending the correct voltage to the Cylinder 4 connector

4. 4

   Check for related broader glow plug circuit codes (such as 3691, 3692, or 3693) which indicate a short to the battery, short to ground, or over-temperature error on the ECU power stage

1. 1

   Disconnect Power

   Disconnect the negative battery cable to prevent accidental shorts while working on the glow plug circuit.

2. 2

   Remove the Faulty Plug

   Disconnect the electrical harness from the Cylinder 4 glow plug. Carefully unthread the glow plug from the cylinder head. (Note: Penetrating oil may be required if the plug is seized, to prevent breaking the tip off in the cylinder head).

3. 3

   Install the New Plug

   Thread the new glow plug into Cylinder 4 by hand to prevent cross-threading, then tighten it to the specific OEM torque rating for your engine model.

4. 4

   Reconnect

   Reattach the electrical connector to the glow plug and reconnect the negative battery cable.

5. 5

   Test and Clear

   Turn the ignition on to cycle the pre-heat system. Use a diagnostic service tool to clear the 3698 fault code.

6. 6

   Control Unit Replacement (If Necessary)

   If the failure persists after a short time of replacing the glow plug and clearing the code, the Glow Plug Control Unit itself is faulty and must be replaced.