Catalytic Converter - Universal

Replacement of universal catalytic converter(s) on a 2017 Maserati Levante 3.0L V6 Twin Turbo, including removal of factory units and installation of universal aftermarket converters with proper welding or clamping.

Warnings

Tools required

Parts

• Universal catalytic converter (bank 1) × 1 — Match cell count and diameter to OEM specifications
• Universal catalytic converter (bank 2) × 1 — Match cell count and diameter to OEM specifications
• Exhaust flange gasket set × 1 — Use OEM specification
• Oxygen sensors (if damaged) × 4 — Use OEM specification or equivalent
• Exhaust hangers (if worn) × 2 — Use OEM specification
• V-band clamps or exhaust adapters × 4 — Match to pipe diameter

Preparation

1. Verify universal catalytic converters are appropriate size and meet emissions requirements for this application
2. Allow exhaust system to cool completely (minimum 2 hours after last operation)
3. Disconnect negative battery terminal and isolate cable
4. Raise vehicle on lift or secure on jack stands at proper lift points
5. Spray all exhaust fasteners, oxygen sensor threads, and flange connections with penetrating oil. Allow 15-30 minutes to soak
6. Remove engine undertray and heat shields to access catalytic converters
7. Document oxygen sensor positions and wiring routing with photos

Procedure

1. 1

   Remove heat shields
   Remove the heat shields covering both catalytic converters. These are typically secured with 10mm bolts. The shields protect surrounding components from extreme heat and must be reinstalled in their original positions.
   Torque spec

   Heat Shield Bolts10 Nm (7 lb-ft)
2. 2

   Disconnect oxygen sensors
   Locate all four oxygen sensors (two upstream and two downstream). Disconnect electrical connectors and carefully remove sensors using an oxygen sensor socket. Turn counterclockwise with steady pressure. If sensors are seized, apply additional penetrating oil and heat. Inspect sensor threads and replace if damaged.
   ⚠Oxygen sensors are fragile. Do not drop or impact sensor tips. Contamination will cause sensor failure.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
3. 3

   Remove exhaust hanger connections
   Locate exhaust hangers supporting the mid-pipe sections downstream of the catalytic converters. Use a pry bar or lubricant to disconnect rubber hangers from their mounting points. This provides flexibility for removal.
   Torque spec

   Hanger Bolts22 Nm (16 lb-ft)
4. 4

   Disconnect downstream exhaust flange
   Locate the exhaust flange connection between the catalytic converter outlet and the mid-pipe or X-pipe. Remove flange bolts using penetrating oil as needed. Support the downstream exhaust section to prevent strain on hangers. Separate the flange connection and remove old gasket material.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
5. 5

   Disconnect upstream connection
   Access the connection between the turbocharger downpipes and the catalytic converter inlets. This may be a flanged connection or V-band clamp. Remove fasteners and carefully separate the joint. The catalytic converters should now be free from the exhaust system.
   Torque spec

   Manifold Nuts35 Nm (26 lb-ft)
6. 6

   Remove catalytic converters
   Carefully lower and remove both catalytic converter assemblies from the vehicle. Note the orientation and position of each converter for reference during universal converter installation. Inspect mounting points and flanges for damage or excessive corrosion.
   ℹ️OEM catalytic converters contain precious metals and should be recycled through proper channels.
7. 7

   Prepare universal converters for installation
   Measure the inlet and outlet pipe diameters of the OEM converters and exhaust system connection points. Cut the factory converter pipes as needed to determine proper universal converter placement. Universal converters will need to be positioned to match OEM location while accommodating oxygen sensor bungs. Test-fit converters before final installation method (welding or clamping).
   ⚠Universal converters must be positioned to maintain proper ground clearance and avoid contact with chassis components, fuel lines, or wiring.
8. 8

   Install oxygen sensor bungs
   Ensure universal catalytic converters have oxygen sensor bungs welded in the correct positions (one upstream, one downstream per converter). Bungs must match OEM sensor spacing to prevent ECU error codes. If bungs are not pre-installed, weld them in position before final converter installation.
   ⚠Oxygen sensor bung placement is critical for proper emissions monitoring. Consult factory specifications for exact positioning.
9. 9

   Install universal catalytic converters
   Position universal converters in place using either welded connections or clamp-on adapters. If welding, disconnect battery, protect fuel and brake lines with heat shields, and ensure proper ventilation. Weld inlet and outlet connections with full penetration welds. If clamping, use high-quality band clamps and exhaust paste to ensure leak-free connections. Verify proper alignment and clearance before final attachment.
   ⚠️Welding requires proper fire prevention measures. Have fire extinguisher accessible and remove flammable materials from work area.
10. 10

    Reinstall oxygen sensors
    Apply anti-seize compound to oxygen sensor threads (threads only, not sensor tip). Install all four oxygen sensors into the universal converter bungs, turning clockwise until snug. Torque to specification using an oxygen sensor socket. Reconnect all electrical connectors and verify wiring is routed away from hot exhaust components.
    ⚠Never apply anti-seize to sensor tips. Contamination will cause permanent sensor damage.
    Torque spec

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

    Reconnect exhaust system
    Reconnect downstream exhaust flange connections using new gaskets. Apply anti-seize to flange bolt threads. Install bolts and torque to specification in a cross-pattern. Reattach exhaust hangers to their mounting points, ensuring proper system alignment and no binding or stress points.
    Torque spec

    Exhaust Flange Bolts45 Nm (33 lb-ft)

    Hanger Bolts22 Nm (16 lb-ft)
12. 12

    Reinstall heat shields
    Reinstall all heat shields in their original positions. Ensure proper clearance between shields and catalytic converters. Torque shield bolts to specification. Verify shields do not contact or rattle against exhaust components.
    Torque spec

    Heat Shield Bolts10 Nm (7 lb-ft)
13. 13

    Reconnect battery and clear codes
    Reconnect negative battery terminal. Use a diagnostic scan tool to clear any stored trouble codes. If oxygen sensor readiness monitors do not set after test drive, verify sensor wiring connections and bung placement.

Reassembly

1. Reinstall engine undertray and any removed protective covers
2. Double-check all exhaust connections for proper torque and alignment
3. Verify all oxygen sensor electrical connections are secure and properly routed
4. Ensure no tools or parts were left in engine bay or under vehicle

Verification

• Start engine and listen for exhaust leaks at all connection points. A hissing sound indicates a leak requiring immediate attention
• Allow engine to reach operating temperature while monitoring for unusual sounds or smells
• Perform test drive and verify normal engine performance with no hesitation or power loss
• Use scan tool to verify all oxygen sensors are reading properly and no DTCs are present
• Perform visual inspection under vehicle after test drive to check for leaks, proper clearance, and secure mounting
• Monitor check engine light status over next 50-100 miles of driving to ensure oxygen sensor readiness monitors complete successfully

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