Massey Ferguson 4363.04 – Engine ECU: SCR catalyst outlet gas temp sensor voltage below normal

The Engine Control Unit is receiving a voltage signal from the SCR (Selective Catalytic Reduction) outlet temperature sensor that is lower than the expected operating range. A "voltage below normal" condition typically indicates a short circuit to ground either within the sensor itself or in its wiring harness.

• 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
• 6700 Series

1. 1

   Inspect the wiring harness and connector leading to the SCR outlet temperature sensor for chafing, melting from exhaust heat, or corrosion that could cause a short to ground.

2. 2

   Disconnect the sensor and use a multimeter to check the sensor's resistance. Check the harness side for continuity to ground on the signal wire.

3. 3

   Inspect the exhaust system around the SCR outlet for leaks at the gaskets or clamps, as physical damage or exhaust leaks can melt the sensor's pigtail.

1. 1

   Cool Down

   Ensure the tractor is turned off and the exhaust system has completely cooled down to prevent severe burns.

2. 2

   Locate the Sensor

   Find the SCR outlet temperature sensor, which is threaded into the exhaust pipe downstream of the SCR catalyst.

3. 3

   Disconnect

   Unplug the sensor's electrical connector from the main engine harness.

4. 4

   Remove the Sensor

   Use a wrench to carefully unscrew the sensor from the exhaust pipe. Note: Penetrating oil may be required if the threads are seized from extreme heat cycling.

5. 5

   Install the New Sensor

   Thread the new sensor into the exhaust pipe and tighten it securely.

6. 6

   Route the Wiring

   Reconnect the electrical connector. Ensure you route the harness exactly like the factory setup to avoid heat soak and vibration failures.

7. 7

   Clear Codes

   Use a diagnostic tool (such as Jaltest or AGCO Wintest) to clear the active 004363.04 fault code from the Engine ECU.