Case IH 19681 – Vehicle Electronic Control Unit (VECU) / Engine Control Module: Power relay high side driver circuit short to battery failure

The control module is detecting unexpected battery voltage (a short to a 12V source) on the high-side driver circuit that controls the power relay. This condition typically occurs when a control wire is shorted to a constant power source, the relay itself has failed/stuck internally, or the control module has an internal driver failure (such as an output transistor stuck open/high).

• Tier 4b
• Tier 4B models
• Puma
• Optum
• Magnum

1. 1

   Read and record all freeze-frame data and related codes with a diagnostic scan tool

2. 2

   Visually inspect the power relay, the relay socket, connectors, and the wiring harness for any signs of physical damage, melting, corrosion, or overheating

3. 3

   Swap the suspect power relay with an identical, known-good relay from another circuit to see if the fault clears or moves

4. 4

   With the key OFF, disconnect the control module connector. Backprobe the relay control wire and measure for continuity or a short between the control wire and battery positive (B+). It should read as infinite or high resistance when disconnected

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the battery to prevent electrical spikes during testing.

2. 2

   Locate the Relay

   Identify the main power relay in the machine's fuse/relay center.

3. 3

   Test/Replace the Relay

   Remove the relay. If the relay swap test (above) resolved the issue, the original relay has a stuck coil or fused contacts. Replace the relay.

4. 4

   Repair the Wiring Harness

   If the relay is good but the circuit test showed a short to battery, trace the wiring harness from the relay socket back to the control module. Locate the chafed or damaged wire that is making contact with a 12V power source and repair/splice the wire.

5. 5

   Module Replacement (Worst Case)

   If the wiring harness tests perfectly (no shorts to battery) and the relay is fully functional, the control module itself has suffered an internal high-side driver failure. The module will need to be replaced and reprogrammed by a dealer.

6. 6

   Verify Repair

   Reconnect the battery, clear the fault codes using a scan tool, and cycle the key to ensure the code does not return.