Case IH F-2634-03 - ECU – Engine Control Unit (ECU A-095): Auxiliary power relay low side driver circuit short to battery failure

The ECU controls the voltage to the auxiliary power relay (K-064). The ECU monitors the low side control circuit of this relay. If the ECU detects a short-to-battery condition on this specific circuit, it triggers this fault code.

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1. 1

   Verify if the fault is currently active; active faults must be diagnosed first before looking into historical codes

2. 2

   Check for related over-temperature codes, specifically DTC 8322 (3440) - 'Auxiliary power relay low side ECU driver circuit over temperature failure', which often accompanies or precedes this failure

3. 3

   Check for an improperly connected external power supply

4. 4

   Inspect the charging system for faults

5. 5

   Evaluate the K-064 auxiliary power relay/solenoid for faults

6. 6

   Inspect the wire harness for a short to a high source or battery

7. 7

   Evaluate the Central Control Unit (CCU) or Universal Control Module (UCM) for faults

1. 1

   Isolate the Relay

   Locate and remove the K-064 Auxiliary Power Relay from the distribution panel.

2. 2

   Test the Relay Coil

   Use a multimeter to check the K-064 relay coil for an internal failure or short. If the relay fails the continuity/resistance test, it must be replaced.

3. 3

   Inspect the Wiring Harness

   If the relay tests good, trace the low side driver circuit wiring harness between the K-064 relay receptacle and the ECU A-095.

4. 4

   Test for Shorts

   Use a multimeter to test the harness for a short circuit to the battery (voltage present on the ground/control side when it shouldn't be).

5. 5

   Repair Wiring

   If a short circuit is indicated during the multimeter test, repair or replace the affected section of the wire harness as required.

6. 6

   Module Testing

   If both the relay and the wiring harness are in good working order, the fault lies within the ECU (A-095) or the Central Control Unit (CCU), which may have suffered internal driver damage (often preceded by the over-temperature code) and will require replacement by a certified Case IH technician.