New Holland ENG 3154 – Engine Control Module (ECM): Grid Heater Relay _Short circuit to Battery

The engine controller has detected that the control circuit for the cold start grid heater relay is receiving unexpected battery voltage. This is typically caused by a wiring short to a power source, a short inside the relay itself, or a failed electrical connector.

• T6.140
• T6.145
• T6.160
• T7.165S
• T7.175
• T7.190
• T7.210
• T7.225
• T8.350
• CX860
• CR960
• CR970
• CR9040
• CR9060
• CR9070
• B90B
• B100B
• B110B
• B115B
• W190B

1. 1

   Inspect the wiring harness running from the Engine ECU to the grid heater relay for chafed wire insulation, melted wires, or pinched harnesses that could bridge the relay control wire to a 12V battery source.

2. 2

   Disconnect the grid heater relay and the ECU harness connectors and check for corrosion, water ingress, or bent pins that could cause a short.

3. 3

   Test the grid heater relay internally with a multimeter to check for a fused or internally shorted relay coil.

4. 4

   With the relay disconnected, turn the key ON and probe the ECU control wire at the relay connector. If it shows 12V when the ECU is not commanding the heater on, the wiring harness is shorted to battery power.

1. 1

   Turn off the machine and disconnect the negative battery cable to prevent accidental arcing.

2. 2

   Locate the grid heater relay.

   Depending on the model, it is typically mounted on the engine rear frame, front frame bracket, or near the battery box.

3. 3

   Disconnect the electrical connector from the grid heater relay.

4. 4

   If the diagnostic tests proved the relay is internally shorted, unbolt the relay from its mounting bracket and install the replacement relay.

5. 5

   If the wiring harness is shorted, carefully unclip the harness from its retaining brackets (e.g., the battery-to-grid heater relay harness). Repair the exposed wire or replace the affected harness section.

6. 6

   Reconnect the grid heater relay electrical connector.

7. 7

   Reconnect the battery.

8. 8

   Use the CNH EASy diagnostic tool (or equivalent scanner) to clear the ENG 3154 fault code from the Engine ECU and verify the repair by cycling the key to trigger the cold start sequence.