New Holland NH 3041 – Engine Controller (Engine ECU / EDC - Electronic Diesel Control): HS Power stage cold start heater relay - SOURCE LOW

The engine control system has detected a "Source Low" condition on the High Side (HS) power stage of the cold start heater relay circuit, typically indicating a short to ground or a severely low voltage condition in the control circuit.

• T5000 series
• T6000 series
• T7000 series
• TM series

1. 1

   Inspect the wiring harness running from the Engine ECU to the cold start heater relay for chafed insulation, melted wires, or pinch points touching the chassis.

2. 2

   Disconnect the cold start heater relay and measure resistance across the control coil pins to check for an internal dead short.

3. 3

   Perform a harness continuity test between the relay's High Side control wire and chassis ground with the relay and Engine ECU disconnected.

4. 4

   Verify ECU jumper configurations (e.g., JP4) for the cold start heater relay are set correctly for the specific machine options.

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the negative battery cable to prevent accidental arcing or ECU damage.

2. 2

   Locate the Relay

   Locate the cold start heater relay. It is typically a heavy-duty relay mounted near the engine intake manifold, the battery box, or within the main engine compartment relay center.

3. 3

   Repair the Harness

   If the diagnostic tests revealed a short in the wiring, trace the wire back to the ECU. Cut out the damaged section of the wire, solder in a new section of equivalent gauge, and seal it with heat-shrink tubing. Secure the harness away from hot engine components or sharp metal edges.

4. 4

   Replace the Relay

   If the relay coil failed the resistance test (internally shorted), unbolt the relay from its mounting bracket, disconnect the heavy-gauge heater wires and the control connector, and install a new OEM relay.

5. 5

   Reassemble and Clear Codes

   Reconnect all connectors and the negative battery cable. Turn the key to the ON position and use a diagnostic tool (such as the CNH Electronic Service Tool) to clear the NH 3041 inactive fault code.

6. 6

   Verify Operation

   Cycle the key in cold conditions to ensure the cold start wait-to-start light illuminates and the relay clicks on without throwing the code again.