Case IH 3442 – Engine Control Unit (ECU) A-095: Auxiliary power relay low side driver circuit short to ground failure.

The Engine Control Unit (ECU) monitors the low side control circuit of the auxiliary power relay (K-064). If it detects a short to ground, it logs this fault. Primary causes include a faulty K-064 relay coil, a short to ground in the low side control circuit wiring, or a faulty/corrupted ECU.

• Steiger T4B
• Case IH Puma Series Tractors
• Case IH 240 Series Axial-Flow Combines
• Other Case IH equipment utilizing Tier 4 engines with the A-095 ECU architecture

1. 1

   Connect the Case IH Electronic Service Tool (EST) to verify if the fault is active or intermittent

2. 2

   Ensure the machine's battery is not connected to an external power supply (like a booster or charger), which can trigger false faults

3. 3

   Remove the K-064 auxiliary power relay and test the internal coil resistance with a multimeter to check for an internal short

4. 4

   With the relay removed and the ECU disconnected, test the low side driver circuit wire for continuity to ground to check for a shorted wire

1. 1

   Disconnect Power

   Turn off the machine and disconnect the negative battery terminal to prevent electrical damage.

2. 2

   Inspect and Replace Relay

   Locate the K-064 Auxiliary Power Relay in the main distribution panel. If the relay coil failed the diagnostic test, replace the relay.

3. 3

   Repair Wiring Harness

   If the harness test showed a short to ground, physically trace the low side circuit wire from the relay panel to the A-095 ECU. Look for pinch points, rubbed insulation, or melted wires touching the chassis. Repair the damaged wire and insulate it properly.

4. 4

   Address the ECU

   If the relay and the wiring harness are both in perfect working order, attempt to reinstall/re-flash the ECU software using the EST. If the software flash fails or the code immediately returns, the ECU A-095 must be replaced.

5. 5

   Clear and Test

   Reconnect the battery, use the EST to clear the fault codes, and run the engine to verify the repair.