Case IH 3511 – Engine Control Unit (ECU) / Dosing Control Unit (DCU): Sensor Supply 3 Circuit - Voltage Below Normal / Shorted to Low Source

The ECU detects that the downstream temperature is rising faster or reading higher than the upstream temperature, indicating the sensors or connectors are swapped. Note: Fault Code 3511 actually designates a 5V reference voltage issue (Sensor Supply 3 Circuit - Voltage Below Normal / Shorted to Low Source).

• Magnum
• Steiger
• Quadtrac
• Optum
• Puma
• Maxxum
• Farmall
• Axial-Flow 7120
• Axial-Flow 7240
• Axial-Flow 8240
• Axial-Flow 9230
• Axial-Flow 9240
• Patriot

1. 1

   Visual Inspection: Trace the wiring harness for the upstream and downstream exhaust gas temperature sensors to check for cross-connected harnesses.

2. 2

   Live Data Monitoring: Connect the Case IH Electronic Service Tool (EST) and monitor live data from a cold start; the upstream sensor should heat up significantly faster.

3. 3

   Voltage Check (If diagnosing the actual 3511 code): Check the 5V reference voltage at the ECU pins (Sensor Supply 3) for shorts to ground or battery voltage.

1. 1

   Cool Down

   Allow the exhaust system to cool completely to avoid severe burns.

2. 2

   Disconnect Power

   Disconnect the negative battery terminal for electrical safety.

3. 3

   Correct the Wiring (If applicable)

   If the physical sensors are in the correct bungs but the wiring is crossed, unplug the connectors and swap them to their correct harness leads.

4. 4

   Correct the Sensors (If applicable)

   If the sensors were threaded into the wrong ports, carefully unscrew both sensors, inspect threads for damage, reinstall in correct locations by hand, and torque to OEM specifications.

5. 5

   Clear and Test

   Reconnect the battery, use the EST to clear inactive fault codes, and run the engine under load at operating temperature to ensure the code does not return.