New Holland ENG 3156 – Engine Control Module (ECM / EDC - Electronic Diesel Control): Grid Heater Relay - No Load

The Engine Control Module (ECM) is commanding the grid heater relay to turn on (usually during a cold start sequence), but the ECM is not detecting any electrical load or current draw on the circuit. This points to an open circuit condition, meaning power is not reaching the grid heater element.

• T6.140
• T6.175
• T7.165S
• T7.175
• T7.190
• T7.210
• T7.225
• T7.290
• T7.315
• T8.350
• T6020
• CR9090
• CX8080
• CX8090
• B90B
• B100B
• B110B
• B115B
• W190B
• Magnum
• Puma

1. 1

   Check the Fuses: The grid heater system draws a massive amount of current and is protected by heavy-duty fuses. Check the 150 Amp Mega Fuse on the main power line, as well as the smaller control circuit fuse (often a 15A mini fuse, designated for the K-023 or K-053 relay depending on the model).

2. 2

   Inspect the Wiring Harness: Visually inspect the wiring harness running from the battery to the grid heater relay, and from the relay to the grid heater element. Look for broken wires, melted insulation, or loose terminal connections.

3. 3

   Test the Relay: Locate the grid heater relay (often mounted on an engine frame bracket or near the starter/alternator harness). Test for voltage at the relay input. Jump the relay to see if the grid heater engages; if it does, the relay itself or the ECM trigger wire is faulty.

4. 4

   Test the Grid Heater Element: Check the grid heater element for continuity using a multimeter. If the element is burnt out (open circuit), it will not draw a load, triggering this code.

1. 1

   Disconnect Power

   Always disconnect the negative battery cable before working on the grid heater circuit, as the main power cable is directly connected to the battery and carries high amperage.

2. 2

   Access the Relay

   Locate the grid heater relay. On many T6 and T7 tractors, it is mounted to an engine frame bracket on the right-hand side. You may need to detach the Air Conditioning (A/C) pipe retaining bracket to access it.

3. 3

   Replace Blown Fuses

   If the 150A mega fuse or the 15A control fuse is blown, unbolt the old fuse and install a new one. (Note: If the mega fuse is blown, check the main power cable for a short to ground before reconnecting power).

4. 4

   Replace the Relay / Harness

   Disconnect the electrical connectors from the grid heater relay. Unbolt the relay bracket and remove the faulty relay. If the wiring harness is corroded or burnt at the connector, remove the damaged harness section (cutting zip ties as necessary) and install a replacement harness. Install the new relay and reconnect the electrical terminals securely.

5. 5

   Reassembly and Clearing Codes

   Reconnect the battery. Turn the key to the ON position to initiate the cold start sequence. The ECM should now detect the load. Clear the stored fault codes using the CNH Electronic Service Tool (EST), or allow the system to clear the active code after a successful start cycle.