Case IH 3606 – Engine ECU (EDC - Electronic Diesel Control) or VCM (Vehicle Control Module): Temperature of Outer control loop - Temperature deviation below Limit

This is an emissions-related fault concerning the Selective Catalytic Reduction (SCR) / Diesel Exhaust Fluid (DEF) system. It indicates that the exhaust gas temperature within the SCR catalyst's 'outer control loop' is reading lower than the expected threshold limit. When this happens, the catalyst cannot reach or maintain the required operating temperature for efficient NOx reduction, which can eventually lead to engine torque derating.

• Magnum
• Maxxum
• Puma
• Steiger
• Patriot Sprayers
• Compact Track Loaders
• TR340

1. 1

   Check for accompanying SCR/DEF codes (such as 3602, 3586-3590, or 3609) that might pinpoint the root cause

2. 2

   Inspect the exhaust system upstream of the SCR catalyst for physical exhaust leaks that could cause a drop in exhaust temperature

3. 3

   Inspect the wiring harness and connector for the Exhaust Gas Temperature (EGT) sensor for melted wires, corrosion, or loose pins

4. 4

   Use the CNH Electronic Service Tool (EST) to monitor live EGT sensor values and compare to ambient temperature when the machine is cold

1. 1

   Connect Diagnostic Tool

   Connect the CNH EST to the machine's diagnostic port to verify code 3606 is active and review freeze-frame data.

2. 2

   Locate the Sensor

   Locate the Exhaust Gas Temperature (EGT) sensor on the exhaust pipe. Depending on the specific FPT engine model, this will be located either just before the SCR muffler or directly on the SCR catalyst housing.

3. 3

   Remove the Sensor

   Disconnect the sensor's electrical connector. Carefully unscrew the EGT sensor from the exhaust bung. (Note: Exhaust sensors frequently seize due to heat cycles; apply penetrating oil and allow it to soak if resistance is high to avoid stripping the threads).

4. 4

   Install New Sensor

   Apply a small amount of anti-seize compound to the threads of the new sensor (if not pre-applied) and install it into the exhaust bung. Torque to the OEM specification found in your specific machine's service manual.

5. 5

   Reconnect and Clear

   Reconnect the electrical harness. Turn the key to the ON position and use the EST to clear the fault codes.

6. 6

   Validation

   Start the engine and perform a forced stationary regeneration, or test-drive the machine under a heavy working load to bring the exhaust up to operating temperature. Verify that the SCR temperature rises appropriately and that code 3606 does not return.