New Holland NH 3058 – Engine ECU: Cold start heater monitoring - SOURCE LOW

The Engine Control Unit (ECU) has detected a low voltage condition, short to ground, or an open circuit on the monitoring circuit for the cold start heater (intake grid heater or thermostart heater). When this code is active, the grid heater will likely fail to operate, resulting in hard starting, extended cranking, and rough idling in cold ambient temperatures.

• T6 Series
• T6.175
• T7 Series
• T7.165S
• T7.175
• T7.190
• T7.210
• T7.225
• T8 Series
• TS/TD Series
• D125C Crawler Dozer
• D150C Crawler Dozer
• LS180.B Skid Steer
• Wheel Loaders

1. 1

   Verify Ambient Temperature: Ensure the temperature is actually cold enough to trigger the system, as the grid heater is only commanded on by the ECU when the ambient/coolant temperature is below a specific threshold.

2. 2

   Check the Grid Heater Fuse: Inspect the high-current fuse protecting the grid heater circuit (often a 200A Mega fuse). A blown fuse will cut power to the heater and can trigger monitoring faults.

3. 3

   Inspect the Grid Heater Relay: Locate the grid heater power relay. Check for corroded terminals, melted connectors, or a stuck open/closed internal contact.

4. 4

   Test the Wiring Harness: Check the wiring harness between the Engine ECU, the grid heater relay, and the heater element itself. Look for chafed wires causing a short to ground ("Source Low") or disconnected plugs.

5. 5

   Test the Heater Element: Measure the resistance of the cold start heater element in the intake manifold to ensure it has not failed open.

6. 6

   Software Configuration: On some models, verify via the instrument cluster or diagnostic tool (e.g., H3 configuration menu) that the grid heater is properly enabled in the software.

1. 1

   Disconnect Power

   Disconnect the negative battery cable before working on the high-current grid heater circuit to prevent accidental shorts.

2. 2

   Replace the Fuse (If Applicable)

   If the 200A grid heater fuse is blown, replace it. Note: Always investigate what caused the fuse to blow (e.g., a shorted heater element or chafed wire) before installing a new one.

3. 3

   Replace the Relay

   If the relay fails to click when commanded, or if it clicks but fails to pass voltage to the heater element, unbolt the heavy-gauge cables from the relay studs, unplug the control connector, and install a new grid heater power relay.

4. 4

   Repair/Replace the Harness

   If the wiring harness is damaged, repair the broken wires using weather-sealed connectors, or install a replacement grid heater relay wiring harness.

5. 5

   Replace the Heater Element

   If the intake heater element is open or shorted internally, remove the intake manifold piping/plate, unbolt the old element, and install a new cold start heater element. Torque the fastening bolts to the specified value in the service manual.

6. 6

   Reassemble and Clear Codes

   Reconnect all cables and the battery. Use a diagnostic tool to clear the NH 3058 fault code from the Engine ECU.

7. 7

   Verify Operation

   Turn the ignition key to the ON position in cold weather and verify that the grid heater indicator light illuminates on the dash and that voltage is reaching the heater element.