Massey Ferguson 626.03 – Engine Control Unit (ECU): Engine Intake Heater High Voltage (ECU)

The engine's control system has detected a voltage signal on the engine intake heater (or thermostart/grid heater) circuit that is higher than the expected normal operating range. This condition typically points to a short to power in the wiring harness, a faulty/stuck-closed intake heater relay, or an internal failure in the intake heater element itself.

• 4710
• 7724S
• 5712SL
• Interim Tier 4 (2012-2015)
• 7722
• 7722S
• 7615
• 5613
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 7616
• 7618
• 5608
• 4708
• 7619
• 7626
• 7726S
• 7624
• 4707
• 4709
• 5711SL
• 7614
• 7718S
• 5610
• 7620
• 7719
• 7714
• 7716S
• T4 (2015-2021)
• 5612
• 7622
• 7720
• Tier 4 (2015-2021)
• 5611
• 7715S
• 5609
• 7724

1. 1

   Locate the air intake heater relay in the fuse/relay block and use a multimeter to check for continuity across the terminals to ensure it is not stuck closed.

2. 2

   With the ignition ON but the engine OFF (and warm enough that pre-heat is not commanded), check the voltage at the intake heater element. Full battery voltage indicates a relay or wiring fault.

3. 3

   Inspect the wiring harness connecting the ECU, the intake heater relay, and the intake heater element for rubbed wires, melted insulation, or shorts to a 12V power source.

4. 4

   Test the resistance of the intake heater element itself to ensure it is not internally shorted.

1. 1

   Disconnect Power

   Disconnect the negative battery terminal to ensure safety while working on the electrical system.

2. 2

   Replace Relay

   If the diagnostic tests point to a stuck relay, pull the old relay from the fuse/relay block and plug in a new OEM relay.

3. 3

   Repair Wiring

   If a short to power is found in the harness, splice and solder the damaged wire, and protect it with heat-shrink tubing and wire loom.

4. 4

   Replace Intake Heater Element

   Locate the intake heater plug/element on the engine intake manifold. Disconnect the electrical screw terminal or spade connector. If your specific engine uses a thermostart style heater (which burns a small amount of fuel), disconnect the fuel return line attached to it. Unthread the old intake heater from the manifold (many use a 7/8"-14 UNF thread). Thread the new intake heater into the manifold and tighten to specification. Reconnect the fuel line (if applicable) and the electrical connection.

5. 5

   Clear Codes

   Reconnect the battery, turn the ignition on, and use a diagnostic scan tool to clear the 000626.03 fault code. Start the engine to verify the code does not return.