Case IH 17588 (F-518408-05) - ECU – Engine Control Module (ECM): Power Relay driver is open circuit only

The control module is attempting to activate the main power relay but is not detecting any electrical current flow through the relay's control circuit. This indicates a broken wire, a disconnected plug, a blown fuse supplying the relay coil, a burned-out relay coil, or a failure of the internal driver inside the control module itself.

• VESTRUM CVX
• Farmall
• Maxxum
• Magnum

1. 1

   Check the Relay: Locate the ECM Main Power Relay. Remove it and test the relay coil for continuity using a multimeter. If the coil shows infinite resistance (OL), the relay is internally open and must be replaced.

2. 2

   Check the Wiring Harness: Inspect the wiring harness between the ECM and the power relay socket. Look for chafed, broken, or corroded wires. Perform a continuity test on the control wire from the ECM pin to the relay socket.

3. 3

   Check Power Supply to the Relay Coil: Ensure that the relay coil is receiving its required ignition/battery voltage when the key is turned on. A blown fuse on this circuit will also cause the ECM to see an "open circuit" on the driver side.

4. 4

   Inspect Connectors: Check the ECM harness connectors and the relay socket for pushed-out pins, spread terminals, or corrosion.

1. 1

   Disconnect Battery

   Always disconnect the negative battery terminal before performing electrical repairs or unplugging the ECM.

2. 2

   Replace Faulty Relay

   If the diagnostic checks reveal an open relay coil, replace the power relay with a new OEM equivalent.

3. 3

   Repair Wiring

   If a broken wire is found between the ECM and the relay, repair the wire using appropriate automotive-grade splices and heat shrink, or replace the affected harness section.

4. 4

   Replace ECM

   If the relay tests good, the wiring harness has perfect continuity, and the relay coil is receiving power, the internal driver inside the ECM has likely failed. The ECM will need to be replaced and reprogrammed by a Case IH dealer.

5. 5

   Clear Codes

   Reconnect the battery, cycle the key, and use a diagnostic scan tool to clear the fault codes and verify the repair.