Case IH 3869-05 - IMM – IMM: IMM: LF antenna 1 error - auxiliary I/O current below normal

The immobilizer system uses a Low Frequency (LF) antenna to energize and read the RFID chip inside the operator's ignition key. The control module is detecting an open circuit, high resistance, or a completely disconnected wire on the LF antenna circuit, preventing the machine from recognizing the key and allowing the engine to start.

• MAGNUM AFS Connect
• Magnum
• Steiger
• Puma
• Optum
• Maxxum
• Axial-Flow

1. 1

   Visually inspect the wiring harness leading to the ignition switch LF antenna ring for chafed wires, pinched harnesses, or disconnected plugs.

2. 2

   Disconnect the antenna coil connector and inspect the pins for corrosion, moisture ingress, or backed-out terminals.

3. 3

   Perform a continuity/resistance test across the two pins of the LF antenna coil using a digital multimeter. If it reads 'OL' (open loop) or infinite resistance, the internal copper windings are broken.

4. 4

   Perform an induction test using an automotive immobilizer coil tester (induction ring) over the ignition slot to see if the IMM module is attempting to pulse the antenna when the key is turned.

1. 1

   Disconnect power

   Turn off the machine and disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Access the ignition switch

   Remove the plastic steering column covers or dashboard trim panels surrounding the ignition key cylinder.

3. 3

   Remove the faulty antenna

   Unplug the electrical connector from the immobilizer antenna ring. Carefully unclip or slide the plastic LF antenna ring off the front of the ignition lock cylinder.

4. 4

   Install the new antenna

   Slide the replacement immobilizer antenna ring over the ignition cylinder until it seats firmly.

5. 5

   Reconnect wiring

   Plug the electrical connector back into the new antenna ring.

6. 6

   Reassemble trim

   Reinstall the steering column shrouds and trim panels.

7. 7

   Test and clear codes

   Reconnect the battery. Insert the programmed ignition key and turn it to the ON position. The immobilizer should now recognize the key. Use the Case IH EASy diagnostic tool or the in-cab Pro 1200 monitor to clear the inactive 3869-05 fault code from the IMM module.