O2 Sensor - Upstream

Replace the upstream oxygen sensor(s) on the 2017 Maserati Levante 3.0L V6 Twin Turbo engine to restore proper air-fuel mixture monitoring and emissions control.

Warnings

Tools required

Parts

• Upstream O2 sensor - Bank 1 × 1 — Use OEM specification
• Upstream O2 sensor - Bank 2 × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and apply parking brake securely
2. Place wheel chocks behind rear wheels
3. Allow engine and exhaust system to cool completely (minimum 60 minutes after engine shutdown)
4. Raise front of vehicle and support on jack stands rated for vehicle weight
5. Remove engine undertray/splash shield if equipped for better access
6. Disconnect negative battery terminal to clear fault codes and prevent false DTCs during replacement

Procedure

1. 1

   Locate upstream O2 sensors
   Identify the upstream O2 sensors on both banks. Bank 1 is the right side (passenger side), Bank 2 is the left side (driver side). The upstream sensors are positioned in the exhaust manifold or front exhaust pipe before the catalytic converters, typically 6-12 inches downstream from the turbocharger outlets. Trace the sensor wiring harness to ensure you're working on the upstream sensors, not the downstream (post-cat) sensors.
2. 2

   Disconnect sensor electrical connectors
   Locate the wiring harness connectors for both upstream O2 sensors. These may be secured with clips or mounted to brackets near the sensor locations. Press the release tab and disconnect each connector. If connectors are corroded or stuck, gently work them free without forcing to avoid damaging the connector pins.
3. 3

   Free wiring harness routing
   Carefully release any clips, ties, or brackets securing the O2 sensor wiring to the exhaust or chassis. Note the exact routing for reinstallation. The wiring must be routed away from hot exhaust components and moving parts. Take photos if needed for reference during reassembly.
4. 4

   Apply penetrating oil to sensor threads
   If sensors show signs of corrosion or have been installed for extended periods, spray penetrating oil around the base threads where the sensor enters the exhaust pipe. Allow 10-15 minutes for penetration. This step helps prevent thread damage during removal.
   ⚠Do not allow penetrating oil to contact the sensor tip or element as this will contaminate and ruin the sensor.
5. 5

   Remove Bank 1 upstream O2 sensor
   Using the O2 sensor socket and ratchet with appropriate extensions, carefully loosen the Bank 1 (right side) upstream sensor. Turn counterclockwise. If sensor resists removal, do not force it - apply more penetrating oil and wait. Once loosened, unthread sensor completely by hand to avoid damaging threads. Keep sensor upright if it will be reused for inspection.
   ⚠Excessive force can strip exhaust threads requiring expensive pipe replacement. If sensor will not turn after multiple attempts with penetrating oil, exhaust heat may be required.
6. 6

   Remove Bank 2 upstream O2 sensor
   Repeat the removal process for the Bank 2 (left side) upstream sensor. Use the O2 sensor socket and ratchet, turning counterclockwise. Remove sensor completely and set aside. Inspect both old sensors for oil contamination, carbon buildup, or physical damage which may indicate other engine issues.
7. 7

   Clean exhaust threads
   Using a wire brush, carefully clean the threads in both exhaust pipe bungs where the sensors mount. Remove any carbon deposits, corrosion, or old anti-seize compound. Ensure threads are clean and undamaged. Do not allow debris to fall into the exhaust system.
   ℹ️Inspect threads for damage. Stripped or cross-threaded bungs must be repaired before sensor installation.
8. 8

   Prepare new sensors
   Remove new O2 sensors from packaging. Apply a thin coat of nickel-based, sensor-safe anti-seize compound to the sensor threads only. Cover approximately 2/3 of the thread length. Do NOT apply anti-seize to the first 2-3 threads or to any part of the sensor tip. Ensure the sensor element and tip remain completely clean.
   ⚠️Anti-seize on sensor tip will cause immediate sensor failure and false readings. Apply only to threads.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
9. 9

   Install Bank 1 upstream O2 sensor
   Thread the new Bank 1 upstream sensor into the exhaust bung by hand, turning clockwise. Thread in carefully to avoid cross-threading. Once hand-tight, use the O2 sensor socket and torque wrench to tighten to specification at 45 Nm (33 lb-ft). Do not over-tighten as this can damage the sensor or exhaust threads.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
10. 10

    Install Bank 2 upstream O2 sensor
    Thread the new Bank 2 upstream sensor into the exhaust bung by hand, turning clockwise. Ensure proper threading, then torque to 45 Nm (33 lb-ft) using the torque wrench and O2 sensor socket. Verify both sensors are secure but not over-torqued.
    Torque spec

    O2 Sensor45 Nm (33 lb-ft)
11. 11

    Route and secure wiring harnesses
    Route both sensor wiring harnesses following the original path documented earlier. Ensure wires are positioned away from hot exhaust components, sharp edges, and moving parts. Secure wiring with all original clips, ties, and brackets. Wiring should have slight slack to prevent tension but not hang loosely.
12. 12

    Connect electrical connectors
    Reconnect the electrical connectors to both upstream O2 sensors. Push connectors fully onto sensors until the locking tab clicks into place. Gently tug each connector to verify secure connection. Ensure no dirt or moisture is present in connector pins.

Reassembly

1. Reinstall engine undertray or splash shield if removed, ensuring all fasteners are secure
2. Lower vehicle from jack stands safely
3. Reconnect negative battery terminal
4. Clear any stored diagnostic trouble codes using appropriate scan tool if available

Verification

• Start engine and verify it runs smoothly without unusual sounds from exhaust area
• Check for exhaust leaks around both sensor installation points - there should be no hissing or exhaust smell
• Verify no check engine light illuminates after 30-60 seconds of engine operation
• Using a scan tool, monitor live O2 sensor data for both banks - sensors should show voltage fluctuations between 0.1-0.9V at normal operating temperature
• Perform a test drive for 10-15 minutes to allow sensors to reach operating temperature and enter closed-loop fuel control
• After test drive, verify no diagnostic trouble codes are present related to O2 sensor circuit or performance

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