Case IH 3526 (F-3234-06) – ECM / EDC or VCM / DCU: Downstream NOx sensor internal failure (Short Circuit Error)

The system has detected an electrical short circuit within the downstream Nitrogen Oxide (NOx) sensor or its immediate circuit.

• VESTRUM CVX
• Magnum 180
• Magnum 200
• Magnum 220
• Magnum 240
• Magnum 250
• Magnum 280
• Magnum 310
• Magnum 340
• Puma 150
• Puma 165
• Puma CVT
• Farmall 40-50 CVT
• Farmall 110A
• Farmall 120A
• Farmall 130A
• Farmall 140A
• Axial-Flow 5140
• Axial-Flow 6140
• Axial-Flow 7140
• Axial-Flow 7240
• Axial-Flow 8240
• Axial-Flow 9240
• Patriot 2250
• Patriot 3240
• Patriot 3340
• Patriot 4440
• Titan 3040
• Titan 3540
• Titan 4040
• Titan 4540

1. 1

   Inspect the wiring harness leading to the downstream NOx sensor for chafing, melting from exhaust heat, or pinch points that could cause a short to ground or battery

2. 2

   Disconnect the downstream NOx sensor and inspect the pins for corrosion, moisture, or damage

3. 3

   Verify that the sensor is receiving the correct supply voltage (typically 12V or 24V depending on the system)

4. 4

   Check the CAN bus communication lines (CAN HI and CAN LO) for proper resistance (approx. 60 ohms across the network)

5. 5

   Isolate the sensor to confirm if the short circuit is internal to the sensor itself

1. 1

   Turn the ignition off and disconnect the battery ground cable to prevent electrical spikes.

   Turn the ignition off and disconnect the battery ground cable to prevent electrical spikes.

2. 2

   Locate the downstream NOx sensor on the exhaust pipe, situated after the SCR catalyst.

   Locate the downstream NOx sensor on the exhaust pipe, situated after the SCR catalyst.

3. 3

   Disconnect the electrical connector for the NOx sensor.

   Disconnect the electrical connector for the NOx sensor.

4. 4

   Using an appropriate sensor socket or wrench, carefully remove the NOx sensor from the exhaust pipe. (Apply penetrating oil beforehand if the sensor is seized due to exhaust heat).

   Using an appropriate sensor socket or wrench, carefully remove the NOx sensor from the exhaust pipe. (Apply penetrating oil beforehand if the sensor is seized due to exhaust heat).

5. 5

   Apply a small amount of anti-seize compound to the threads of the new NOx sensor (avoid getting any on the sensor probe).

   Apply a small amount of anti-seize compound to the threads of the new NOx sensor (avoid getting any on the sensor probe).

6. 6

   Install the new downstream NOx sensor and torque it to the manufacturer's specification.

   Install the new downstream NOx sensor and torque it to the manufacturer's specification.

7. 7

   Route the sensor wiring away from extreme heat sources and reconnect the electrical plug.

   Route the sensor wiring away from extreme heat sources and reconnect the electrical plug.

8. 8

   Reconnect the battery, turn the ignition on, and use a diagnostic scan tool to clear the inactive 3526 fault code.

   Reconnect the battery, turn the ignition on, and use a diagnostic scan tool to clear the inactive 3526 fault code.

9. 9

   Start the engine and allow it to reach operating temperature to verify the code does not return and that the SCR system is dosing correctly.

   Start the engine and allow it to reach operating temperature to verify the code does not return and that the SCR system is dosing correctly.