Massey Ferguson 4357.03 – Engine Control Unit (ECU): DEF Injector Supply Pipe Heater Resistance Is High (ECU)

The control module has detected an abnormally high electrical resistance in the heater circuit for the DEF injector supply line. High resistance typically points to an open circuit, a broken heater wire inside the line, a damaged connector, or a blown relay/fuse.

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

1. 1

   Visual Inspection: Trace the DEF supply line (running from the DEF pump module to the DEF doser/injector on the exhaust). Look for chafing, kinks, or areas where the line may have rubbed against hot exhaust components or sharp frame edges.

2. 2

   Connector Check: Disconnect the electrical pigtail for the DEF supply line heater. Inspect the pins for corrosion, moisture, or pushed-out terminals.

3. 3

   Resistance Test: Using a multimeter, measure the resistance across the heater element pins on the DEF line side. If the reading shows 'OL' (Open Limit) or infinite resistance, the heating element inside the line is broken and the line must be replaced.

4. 4

   Relay/Power Check: Check the DEF line heater relay (often monitored by the ECU) and associated fuses to ensure power is actually being sent to the circuit.

1. 1

   Preparation

   Turn off the tractor, remove the key, and disconnect the negative battery cable. Ensure the exhaust system has cooled down.

2. 2

   Clean the Area

   Clean the quick-connect fittings at the DEF pump module and the DEF doser injector to prevent dirt from entering the SCR system.

3. 3

   Disconnect Electricals

   Unplug the electrical connector for the DEF supply line heater.

4. 4

   Disconnect Fluid Lines

   Using a DEF-rated line wrench or by depressing the quick-release tabs, disconnect the DEF supply line from the pump and the injector. Note: Have a clean rag ready to catch any residual DEF fluid. Do not let DEF spill onto electrical connections as it is highly corrosive.

5. 5

   Remove the Line

   Unclip the line from its routing brackets and remove it from the tractor.

6. 6

   Install the New Line

   Route the new heated DEF supply line exactly as the old one was routed. Ensure it is secured away from sharp edges and extreme heat sources.

7. 7

   Reconnect

   Snap the fluid quick-connects into place (listen for the click) and plug in the electrical connector.

8. 8

   Reassemble and Clear Codes

   Reconnect the battery. Use a diagnostic tool (such as WinEEM4 or an equivalent dealer tool) to clear the 004357.03 fault code.

9. 9

   Prime and Test

   Start the engine and allow the DEF system to prime. Verify that no leaks are present and that the fault code does not return.