how to tell if the catalytic converter is bad on my BMW 3 Series E90/E91 (2005-2012)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the parking brake is engaged.
• Disconnect the battery to ensure safety during repairs.

2. Remove the Catalytic Converter

• Tools Required: Socket set, torque wrench, penetrating oil.
• Sub-steps:
  1. Apply penetrating oil to the exhaust bolts to loosen them if rusted.
  2. Remove the exhaust hangers to lower the exhaust system.
  3. Unscrew and detach the catalytic converter from the exhaust manifold and the pipe.
  4. Carefully remove the catalytic converter from the vehicle.

3. Inspect and Replace

• Tools Required: None additional.
• Sub-steps:
  1. Inspect the old catalytic converter for blockage or internal damage (e.g., rattling sound).
  2. Replace with a new catalytic converter if damaged or clogged.
  3. Ensure the new catalytic converter is compatible with the E90/E91 models.

4. Reinstall Exhaust System

• Tools Required: Torque wrench.
• Sub-steps:
  1. Position the new catalytic converter in place and attach it to the exhaust manifold and pipe.
  2. Tighten the bolts to the manufacturer’s specified torque settings.
  3. Reinstall the exhaust hangers.

5. Final Steps

• Reconnect the battery.
• Clear any error codes using an OBD-II scanner.