New Holland ENG 2555 – ENG (Engine Control Module / Engine ECU): Intake Air Heater 1 Circuit Voltage too high

The ECM has detected that the voltage on the Intake Air Heater 1 control circuit is higher than expected. This almost always indicates a short to a power source (battery voltage) in the wiring harness, a failed/shorted intake air heater relay, or a faulty ECM driver.

• tractors
• wheel loaders
• excavators
• combines

1. 1

   Inspect the wiring harness running from the Engine ECU to the Intake Air Heater Relay for chafed wires, melted insulation, or rubbing against a 12V/24V power source.

2. 2

   Disconnect the control wires from the ECM and test the Intake Air Heater Relay for an internal short to power within the relay coil using a multimeter.

3. 3

   With the relay disconnected and the key ON, measure the voltage on the ECM signal wire. If it reads battery voltage when not commanded, the harness is shorted to power.

4. 4

   Inspect the heavy-gauge wires at the intake air heater element to ensure the main power feed hasn't melted into the control wiring.

1. 1

   Disconnect Power

   Turn off the machine's ignition and disconnect the negative battery cable. The intake air heater circuit carries very high amperage, and working on it live poses a severe fire and shock risk.

2. 2

   Locate the Relay

   Find the Intake Air Heater Relay, which is typically mounted on the engine block near the intake manifold or on the firewall.

3. 3

   Repair Wiring (If Applicable)

   If the harness was found to be shorted to power during diagnostics, splice in a new section of wire using weather-sealed heat-shrink connectors, or replace the affected harness section.

4. 4

   Remove the Faulty Relay

   Unbolt the heavy-gauge battery and heater cables from the relay's large terminals. Then, disconnect the smaller ECM control wires. Remove the mounting bolts securing the relay to the chassis/engine.

5. 5

   Install the New Relay

   Mount the replacement OEM relay. Reconnect the ECM control wires, followed by the heavy-gauge power cables. Torque the terminal nuts to the manufacturer's specification (do not overtighten, as this can crack the relay housing).

6. 6

   Reassemble and Clear Codes

   Reconnect the negative battery cable. Turn the key to the ON position and use a diagnostic tool (or the machine's onboard diagnostic menu) to clear the ENG 2555 fault code. Cycle the key and verify the code does not return.