Case IH 158-04 - ICM – ICM: Vkey line in fault (short to ground - blown fuse)

The system has detected that the ignition power circuit (Vkey) has shorted directly to a ground source, which has subsequently caused the circuit's protective fuse to blow.

• MAGNUM AFS Connect
• Magnum 400 AFS Connect

1. 1

   Inspect the fuse panel to identify the specific fuse responsible for the Instrument Cluster (ICM) Vkey power and confirm it is blown. Do not replace it yet.

2. 2

   Perform a harness isolation test by disconnecting the main wiring harness connector from the back of the Instrument Cluster.

3. 3

   Using a digital multimeter, measure the resistance between the Vkey (ignition power) pin on the harness connector and a known good chassis ground.

4. 4

   Determine the short location: continuity to ground on the harness side indicates a chafed or pinched wiring harness, while no continuity indicates an internal short within the Instrument Cluster.

1. 1

   Disconnect Power

   Turn the ignition key to the OFF position and disconnect the machine's battery to prevent further electrical damage.

2. 2

   Trace the Harness

   If the harness is shorted, visually inspect the wiring harness routing from the instrument cluster down through the steering column/console area to the fuse panel. Look for areas where the wire loom may have rubbed against metal brackets or where wires have been pinched.

3. 3

   Repair the Wiring

   If a chafed wire is found, cut out the damaged section, splice in a new section of wire using weatherproof heat-shrink butt connectors, and re-wrap the harness with anti-abrasion tape.

4. 4

   Replace the Module

   If the cluster is shorted (the harness tests perfectly fine but the fuse blows the moment the cluster is plugged in), the internal circuitry of the ICM has failed. Remove the mounting screws securing the cluster to the console and install a replacement unit.

5. 5

   Replace the Fuse

   Insert a new fuse of the exact same amperage rating into the blown slot in the fuse panel.

6. 6

   Verify Repair

   Reconnect the battery, turn the ignition key to the ON position, and verify that the instrument cluster powers up successfully without blowing the fuse. Ensure the 158-04 fault code changes from 'Active' to 'Inactive' and clear it from the system.