Case IH F-2634-31 - ECU – Engine Control Unit (ECU A-095): Auxiliary power relay low side ECU driver circuit over temperature failure

The Electronic Control Unit (ECU) has detected an over-temperature or over-current condition on the low-side control circuit that grounds the auxiliary power relay. This occurs when the current draw exceeds safe limits, usually due to a short to battery voltage in the wiring harness or a failing relay coil drawing excessive amperage.

• MAGNUM AFS Connect
• Magnum AFS Connect Tractors (e.g., Magnum 400)
• 240 Series Axial-Flow Combines (e.g., 7240, 8240, 9240)
• Austoft Sugarcane Harvesters (e.g., A8800, A9900)

1. 1

   Verify the fault status using the Case IH Electronic Service Tool (EST) to see if it is currently active or inactive/intermittent.

2. 2

   Locate the Auxiliary Power Relay in the Main Distribution Panel (MDP), often on the right cab pillar (designated as Relay #12, K-062, or K-064).

3. 3

   Remove the relay and measure the resistance across the relay coil pins using a multimeter. A dead short or abnormally low resistance indicates a faulty relay.

4. 4

   With the relay removed and battery connected, test the low-side control circuit wire (the pin in the relay socket leading back to the ECU) for unwanted voltage to check for a short to battery.

5. 5

   Visually inspect the cab main harness circuits running from the MDP to the ECU A-095 for chafing, melted insulation, or improper aftermarket accessory splices.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the negative battery cable to prevent further electrical damage during testing.

2. 2

   Access the MDP

   Open the Main Distribution Panel and remove the Auxiliary Power Relay (K-062 / K-064).

3. 3

   Replace Faulty Relay

   If the diagnostic checks revealed the relay coil was shorted or out of specification, replace the relay with a new OEM unit.

4. 4

   Repair Wiring

   If the relay tested fine but a short to battery was found in the harness, trace the specific wire from the MDP back to the ECU A-095 connector. Repair or replace the damaged section of the wiring harness where the short is occurring.

5. 5

   Reassemble and Clear Codes

   Reinstall the relay, reconnect the battery, and connect the EST. Clear the inactive fault codes.

6. 6

   Test Operation

   Cycle the key and run the machine. If the fault immediately returns and the wiring and relay are confirmed to be in perfect condition, the internal driver inside ECU A-095 has likely failed permanently due to the over-temperature event. In this case, the ECU A-095 must be replaced and reprogrammed by a dealer.