New Holland NH 3131 – Engine Control Unit (ECU) / Engine Control Module (ECM): ECU: Self Test Shutoff Paths (Start Up) - NOT PLAUSIBLE / Grid Heater Always Switched On

The ECU detected that the previous engine shutdown process was improper (e.g., power failed or master disconnect turned off too early), or the intake manifold grid heater is receiving continuous power due to a stuck/welded relay.

• T6000 Series (T6010, T6020, T6030, etc.)
• T7 Series (T7.170, T7.210, etc.)
• T8 Series
• TS/TM series
• W190B
• E385
• E485

1. 1

   If diagnosing ECU Shutoff Paths: Interview the operator to determine if the machine stalled, the battery died, or the master battery disconnect was thrown immediately after turning the key off.

2. 2

   If diagnosing ECU Shutoff Paths: Inspect the main ECU power and ground cables at the battery and the ECU harness for loose, corroded, or damaged terminals.

3. 3

   If diagnosing ECU Shutoff Paths: Verify that the main ECU power relay is not dropping out intermittently due to vibration.

4. 4

   If diagnosing Grid Heater Always Switched On: Carefully feel the intake manifold near the grid heater. If it is excessively hot long after the cold-start cycle should have ended, the heater is stuck on.

5. 5

   If diagnosing Grid Heater Always Switched On: Look for related secondary codes such as 3154 (Grid heater relay - short circuit to battery) or 3156 (Grid heater relay - no load).

6. 6

   If diagnosing Grid Heater Always Switched On: Remove the grid heater relay and test for continuity across the high-current load terminals. If there is continuity while unplugged, the internal contacts are welded shut.

1. 1

   Clear fault code

   If repairing the Shutoff Path Error: Clear the fault code using a diagnostic scan tool (or via the machine's onboard diagnostic menu).

2. 2

   Cycle ignition

   If repairing the Shutoff Path Error: Perform a proper key-on / key-off cycle. Turn the ignition on, wait 10 seconds, turn it off, and wait for the ECU to fully power down (listen for the main relay to click off).

3. 3

   Replace relay and clean grounds

   If repairing the Shutoff Path Error: If the code returns immediately on startup, replace the main ECU power relay and clean all battery-to-ECU ground connections.

4. 4

   Instruct operators

   If repairing the Shutoff Path Error: Instruct operators to always use the ignition key to shut down the engine and wait at least 30 seconds before turning off the master battery disconnect switch.

5. 5

   Disconnect power

   If repairing the Grid Heater Error: Immediately remove the grid heater relay or disconnect the heavy-gauge wire at the grid heater to prevent battery drain, alternator strain, or intake manifold damage.

6. 6

   Replace relay

   If repairing the Grid Heater Error: Install a new OEM grid heater power relay.

7. 7

   Inspect harness

   If repairing the Grid Heater Error: Check the grid heater wiring harness for melted insulation caused by the continuous high-current draw. Replace the harness if the wires are brittle or exposed.

8. 8

   Verify repair

   If repairing the Grid Heater Error: Reconnect power, start the tractor, and verify that the grid heater cycles off after the initial cold-start warmup period.