Case IH 3981 – Engine Control Module (ECM): After run relay low side driver circuit open or short to ground failure

The control module has detected a fault on the ground-side (low side) control circuit of the after-run relay. The circuit is either physically broken (open) or has chafed and is touching a ground source (short to ground), preventing the module from properly energizing or de-energizing the relay.

• Steiger T4B
• Case IH 240 Series Axial-Flow Combines
• Case IH Magnum Tractors

1. 1

   Check the wiring harness between the ECM and the after-run relay socket for broken wires (open circuit) or rubbed insulation causing a short to ground

2. 2

   Test the after-run relay for an internal short circuit or failure

3. 3

   Inspect the fuses associated with the engine relays (specifically the 5 Amp after-run relay fuse and the 25 Amp Engine Aux Relay fuse)

4. 4

   Verify battery voltage and alternator output, as voltage drops during the after-run phase can trigger relay faults

1. 1

   Power Down

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

2. 2

   Locate the Relay

   Access the machine's main fuse and relay distribution box. Locate the 'After Run Relay' (often a 5-amp micro-relay) using the panel diagram.

3. 3

   Inspect the Socket

   Pull the relay and inspect the socket terminals for corrosion, pushed-out pins, or signs of melting.

4. 4

   Circuit Testing

   Using a digital multimeter, check the continuity of the low-side driver wire from the relay socket back to the ECM harness connector. Test this same wire for continuity to ground to rule out a short.

5. 5

   Repair Wiring / Replace Relay

   If the wiring is damaged, repair the harness. If the wiring tests good, the relay itself has likely failed internally and must be replaced.

6. 6

   Reassembly and Clearing

   Install the new relay, reconnect the battery, and use a diagnostic tool to clear the inactive DTC 5971. Cycle the key on and off, waiting for the after-run sequence to complete, to ensure the code does not return.