Replace the catalytic converter on a 2016-2024 Hyundai Tucson with 2.5L I4 AWD engine to meet California emissions standards.

Warnings

Tools required

Parts

• CARB-compliant catalytic converter assembly (California legal) × 1 — Use OEM specification or CARB Executive Order approved aftermarket
• Exhaust flange gasket set × 1 — Use OEM specification
• Exhaust flange nuts/bolts × 1 — Use OEM specification
• O2 sensor (if damaged or over 100k miles) × 1 — Use OEM specification

Preparation

1. Verify the replacement catalytic converter has valid CARB Executive Order approval for California use
2. Park vehicle on level surface and engage parking brake
3. Allow exhaust system to cool completely (minimum 2 hours after last operation)
4. Raise vehicle securely on jack stands at manufacturer-specified lift points
5. Spray all exhaust flange bolts and O2 sensor threads with penetrating oil
6. Disconnect negative battery terminal to prevent O2 sensor fault codes during service

Procedure

1. 1

   Remove heat shields
   Locate and remove any exhaust heat shields covering the catalytic converter area using a 10mm socket. There are typically 2-3 shields in this area. Keep track of shield mounting locations for reinstallation.
   Torque spec

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

   Disconnect upstream O2 sensor
   Locate the upstream (pre-catalytic converter) oxygen sensor. Disconnect the electrical connector by pressing the release tab. Using an O2 sensor socket, carefully unthread the sensor counterclockwise. If sensor is seized, apply heat to the bung area (not the sensor itself) and retry. Inspect sensor condition to determine if reuse is acceptable.
   ⚠Do not use excessive force on O2 sensor. If seized, apply heat to exhaust pipe around the sensor bung, not directly to the sensor body.
   Torque spec

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

   Disconnect downstream O2 sensor
   Locate the downstream (post-catalytic converter) oxygen sensor. Disconnect the electrical connector and remove the sensor using an O2 sensor socket. Store sensors in a clean area if reusing.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
4. 4

   Support catalytic converter
   Position a jack or support stand under the catalytic converter to support its weight during removal. The converter assembly weighs approximately 15-20 lbs and should not be allowed to hang by exhaust hangers.
   ℹ️Have an assistant help support the catalytic converter or use an adjustable exhaust support jack.
5. 5

   Remove front exhaust flange connection
   Locate the front flange connection between the exhaust manifold and catalytic converter. Remove the flange bolts/nuts (typically 2 per connection) using a 14mm socket. If bolts are seized, apply heat and additional penetrating oil. Remove and discard the old gasket.
   ⚠Exhaust studs can break if excessive force is applied to severely corroded fasteners. Apply heat carefully if needed.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
6. 6

   Remove rear exhaust flange connection
   Locate the rear flange connection between the catalytic converter and mid-pipe/resonator. Remove the flange bolts using a 14mm socket. Separate the connection and remove the old gasket.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
7. 7

   Disconnect exhaust hangers
   Remove the rubber exhaust hanger mounts that support the catalytic converter. Use a pry bar or exhaust hanger tool to slide the hangers off their mounting points. Note the orientation for reinstallation.
   Torque spec

   Hanger Bolts20 Nm (15 lb-ft)
8. 8

   Remove catalytic converter assembly
   With all connections and supports removed, carefully lower and remove the catalytic converter assembly from the vehicle. Maneuver around suspension components and brake lines as needed.
9. 9

   Clean flange surfaces
   Use a wire brush to thoroughly clean all exhaust flange mating surfaces on both the manifold and mid-pipe connections. Remove all carbon deposits and old gasket material. Inspect flanges for cracks or damage. Clean O2 sensor bung threads with a thread chaser if available.
   ℹ️Proper flange surface preparation is critical to prevent exhaust leaks.
10. 10

    Prepare new catalytic converter
    Verify the new catalytic converter has CARB Executive Order labeling clearly visible. Compare physical dimensions and mounting points to the old unit. Install new flange gaskets onto the new converter. Apply anti-seize compound to O2 sensor threads (threads only, not the sensor tip).
    ⚠Do not get anti-seize compound on the O2 sensor tip as this will contaminate the sensor and cause failure.
11. 11

    Install new catalytic converter
    Position the new catalytic converter assembly into place, ensuring proper orientation with flow direction arrows pointing toward rear of vehicle. Support the converter with a jack while aligning mounting points. Attach exhaust hangers to their rubber mounts.
    Torque spec

    Hanger Bolts20 Nm (15 lb-ft)
12. 12

    Connect front flange
    Align the front flange with the exhaust manifold connection. Ensure the new gasket is properly seated. Install flange bolts/nuts and tighten in a cross-pattern to proper torque specification. Apply anti-seize to bolt threads before installation.
    ℹ️Tighten flange bolts in a cross-pattern to ensure even gasket compression and prevent leaks.
    Torque spec

    Exhaust Flange Bolts45 Nm (33 lb-ft)
13. 13

    Connect rear flange
    Align the rear flange with the mid-pipe connection. Install new gasket and flange bolts. Apply anti-seize to bolt threads and tighten in a cross-pattern to proper torque specification.
    Torque spec

    Exhaust Flange Bolts45 Nm (33 lb-ft)
14. 14

    Install oxygen sensors
    Apply a thin coat of anti-seize compound to O2 sensor threads only (avoid the sensor tip). Thread both upstream and downstream O2 sensors into their bungs by hand first to avoid cross-threading. Tighten to proper torque specification using an O2 sensor socket. Reconnect electrical connectors ensuring they click securely.
    ⚠Start O2 sensors by hand for at least 3-4 complete turns to ensure proper thread engagement before using tools.
    Torque spec

    O2 Sensor45 Nm (33 lb-ft)
15. 15

    Reinstall heat shields
    Reinstall all heat shields in their original positions. Tighten heat shield bolts to proper torque specification. Ensure shields have proper clearance and do not contact moving components.
    Torque spec

    Heat Shield Bolts10 Nm (7 lb-ft)

Reassembly

1. Reconnect negative battery terminal
2. Lower vehicle from jack stands
3. Double-check all fasteners are tightened to specification
4. Verify all electrical connectors are properly seated

Verification

• Start engine and listen for exhaust leaks at all flange connections. A hissing sound indicates a leak requiring re-torquing or gasket replacement
• Allow engine to reach operating temperature and verify no unusual sounds or rattles from exhaust system
• Check for exhaust odors in cabin which would indicate a leak
• Use OBD-II scanner to verify no oxygen sensor fault codes are present (codes may take 1-2 drive cycles to clear)
• Perform a visual inspection under the vehicle with engine running to check for visible exhaust leaks
• Verify CARB Executive Order label is visible on installed catalytic converter for compliance documentation

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