Case IH 3952 – Engine Control Unit (ECU / EDC): Physical Range check low / Exhaust Gas Temperature 1 Sensor Signal Too Low

The Engine Control Unit (ECU) is receiving a voltage or resistance signal from the Exhaust Gas Temperature (EGT) Sensor 1 that falls below the physically possible operating range. This condition typically points to a short to ground in the sensor wiring, an open circuit, or a completely failed sensor.

• Farmall 100C
• Farmall 105A
• Farmall 105C
• Farmall 105U
• Farmall 110A
• Farmall 110C
• Farmall 110U
• Farmall 115A
• Farmall 115C
• Farmall 115U
• Farmall 120U
• Maxxum 120
• Maxxum 125
• Maxxum 130
• Maxxum 140
• Puma 140
• Steiger series
• Combine 5130
• Combine 5140
• Combine 7130
• Combine 7140
• Combine 7150
• Combine 7230
• Combine 7240
• Combine 7250
• Combine 9230
• SR175
• L220
• 121F
• 21F
• 221F
• 321F
• 580 ST
• 590 ST
• 695 ST
• 750M

1. 1

   Inspect the wiring harness and the connector leading to Exhaust Gas Temperature Sensor 1 (usually located upstream on the exhaust/DPF assembly) for chafing, melting, corrosion, or disconnected pins.

2. 2

   Use a multimeter to check for a short to ground or an open circuit in the signal wire between the sensor connector and the Engine ECU.

3. 3

   Measure the resistance across the sensor's pins. If the resistance is completely open (infinite) or shorted (zero), the sensor has failed internally.

1. 1

   Cool Down

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

2. 2

   Disconnect Power

   Disconnect the negative battery terminal to protect the ECU.

3. 3

   Locate the Sensor

   Find Exhaust Gas Temperature Sensor 1 on the exhaust pipe/manifold.

4. 4

   Disconnect

   Unplug the 2-pin electrical connector from the sensor.

5. 5

   Removal

   Use a suitable wrench to carefully unthread the sensor from the exhaust bung. (Note: Penetrating oil may be required if the sensor is seized from heat cycles).

6. 6

   Installation

   Apply a small amount of high-temp anti-seize to the threads of the new sensor (if not already pre-applied by the manufacturer) and thread it into the exhaust bung. Tighten to the OEM specified torque.

7. 7

   Reconnect

   Plug the 2-pin electrical connector back into the harness.

8. 8

   Clear Codes

   Reconnect the battery, turn the key on, and use a diagnostic scan tool to clear the 3952 fault code from the Engine ECU. Start the engine and verify the code does not return.