Iveco 601 – Engine Control Unit (ECU) / EDC: The fault signal circuit or loss of activity of the oxygen sensor 1

The engine control system has detected that the upstream oxygen sensor (Lambda sensor 1, located before the catalytic converter) is either not sending a signal, sending an implausible signal, or has completely lost activity. This prevents the engine from accurately monitoring the exhaust gases to adjust the air-fuel mixture.

• Iveco Daily (Mk4, Mk5, Mk6)
• Iveco Stralis
• Iveco Eurocargo
• Iveco Massif

1. 1

   Inspect the wiring harness leading to Oxygen Sensor 1 for melted wires, chafing, or breaks.

2. 2

   Disconnect the sensor plug and check for corrosion, moisture, or loose pins. Clean with electrical contact cleaner if necessary.

3. 3

   Check for exhaust leaks upstream of the sensor, which can introduce unmetered oxygen into the exhaust stream.

4. 4

   Remove and carefully clean the sensor tip, as heavy soot or carbon buildup can block the sensor's sampling ports.

5. 5

   Look for accompanying heater circuit codes (e.g., 0602 or 0604). If the sensor's internal heater fails, it will not reach operating temperature and will lose activity.

1. 1

   Prep the Vehicle

   Disconnect the negative battery terminal. Ensure the exhaust system has completely cooled down to prevent burns.

2. 2

   Locate the Sensor

   Locate Oxygen Sensor 1 (the upstream sensor, positioned between the engine exhaust manifold and the catalytic converter/DPF).

3. 3

   Disconnect

   Unplug the sensor's electrical connector from the vehicle's wiring harness.

4. 4

   Remove the Sensor

   Spray penetrating oil on the base of the sensor threads and let it sit for a few minutes. Use a dedicated oxygen sensor socket (usually 22mm or 7/8") and a breaker bar to carefully unscrew the sensor.

5. 5

   Prepare the New Sensor

   Check if the new sensor has anti-seize compound pre-applied to the threads (many OEM Bosch sensors do). If not, apply a small amount of high-temp anti-seize to the threads only, being careful not to get any on the sensor tip.

6. 6

   Install

   Thread the new sensor in by hand to prevent cross-threading, then tighten it to the manufacturer's specified torque.

7. 7

   Reconnect

   Plug the electrical connector back into the harness, ensuring it clicks securely into place. Route the wire away from direct contact with the hot exhaust pipe.

8. 8

   Clear Codes

   Reconnect the battery, turn the ignition on, and use an OBD/EDC diagnostic scan tool to clear the 0601 fault code.

9. 9

   Test Drive

   Start the engine, let it reach operating temperature, and test drive the vehicle to ensure the check engine/EDC light does not return.