Catalytic Converter - California

Replace the California-spec catalytic converter assembly on a 2014-2019 Toyota Corolla 1.8L, including removal and installation of oxygen sensors and exhaust connections.

Warnings

Tools required

Parts

• California-spec catalytic converter assembly with manifold × 1 — Use CARB-certified replacement meeting CA emissions standards
• Exhaust manifold to catalytic converter gasket × 1 — Use OEM specification
• Catalytic converter to intermediate pipe gasket × 1 — Use OEM specification
• Exhaust flange nuts (if corroded) × 4 — M10 nuts
• Heat shield bolts (if corroded) × 3 — M8 bolts

Preparation

1. Ensure engine and exhaust system are completely cold to the touch
2. Park vehicle on level surface, engage parking brake, and place wheel chocks behind rear wheels
3. Disconnect negative battery terminal to prevent O2 sensor fault codes during removal
4. Raise front of vehicle and secure on jack stands rated for vehicle weight
5. Spray all exhaust flange bolts, hanger bolts, and O2 sensor threads with penetrating oil and allow to soak for 15-30 minutes

Procedure

1. 1

   Remove heat shields
   Remove the heat shields covering the catalytic converter and exhaust manifold. There are typically 3 bolts securing the upper heat shield. Use 10mm socket to remove bolts. Set heat shields aside for reinstallation.
   Torque spec

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

   Disconnect upstream oxygen sensor (Air-Fuel Ratio Sensor)
   Locate the upstream oxygen sensor (A/F sensor) on the catalytic converter near the manifold connection. Disconnect the electrical connector by pressing the release tab. Using a 22mm oxygen sensor socket, carefully loosen and remove the sensor. Inspect sensor condition and threads.
   Torque spec

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

   Disconnect downstream oxygen sensor
   Locate the downstream oxygen sensor on the rear of the catalytic converter assembly. Disconnect electrical connector and use 22mm oxygen sensor socket to remove sensor. Keep sensors organized and protected from impact damage.
   Torque spec

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

   Remove catalytic converter to intermediate pipe connection
   Locate the two-bolt flange connection where catalytic converter meets the intermediate exhaust pipe. Use 14mm socket to remove the two flange bolts and separate the joint. You may need to use a pry bar to gently separate the flanges. Remove and discard the old gasket.
   Torque spec

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

   Remove exhaust hangers
   Locate the rubber exhaust hangers supporting the catalytic converter assembly. Remove hanger bolts using 14mm socket or carefully pry the rubber hangers off their mounts to allow catalytic converter to drop free.
   Torque spec

   Hanger Bolts19 Nm (14 lb-ft)
6. 6

   Disconnect catalytic converter from exhaust manifold
   From under the vehicle, locate the two-bolt flange connection between the exhaust manifold and catalytic converter inlet. Use 14mm socket to remove both flange bolts. Support the catalytic converter assembly as you remove the final bolt. Carefully lower the catalytic converter assembly from the vehicle. Remove and discard old gasket.
   Torque spec

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

   Prepare mounting surfaces
   Use wire brush to thoroughly clean all exhaust flange surfaces on the manifold and intermediate pipe. Remove all carbon deposits, old gasket material, and corrosion. Inspect flange surfaces for warping or damage. Clean oxygen sensor bung threads with wire brush if reusing sensors.
8. 8

   Install new catalytic converter to manifold
   Apply thin coat of anti-seize to exhaust flange bolt threads. Position new exhaust gasket on manifold flange (do not use sealant). Lift new catalytic converter assembly into position and align with manifold flange. Start both flange bolts by hand to ensure proper alignment, then tighten to specification using torque wrench.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
9. 9

   Connect catalytic converter to intermediate pipe
   Position new gasket on the catalytic converter outlet flange. Align intermediate pipe and start both flange bolts by hand. Apply anti-seize to bolt threads. Torque both bolts to specification in alternating pattern.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
10. 10

    Secure exhaust hangers
    Reconnect exhaust system to rubber hangers or install hanger bolts. Ensure exhaust system hangs with proper clearance from body, frame, and suspension components. Torque hanger bolts to specification if applicable.
    Torque spec

    Hanger Bolts19 Nm (14 lb-ft)
11. 11

    Install oxygen sensors
    Apply small amount of anti-seize compound to oxygen sensor threads only - avoid getting anti-seize on sensor tip. Hand-thread upstream oxygen sensor (A/F sensor) into catalytic converter bung, then tighten to specification using oxygen sensor socket and torque wrench. Repeat for downstream sensor. Reconnect both electrical connectors ensuring they click securely.
    Torque spec

    O2 Sensor45 Nm (33 lb-ft)
12. 12

    Reinstall heat shields
    Position heat shields over catalytic converter and exhaust manifold. Install all bolts and tighten to specification. Ensure heat shields do not rattle or contact other components.
    Torque spec

    Heat Shield Bolts10 Nm (7 lb-ft)

Reassembly

1. Reconnect negative battery terminal
2. Lower vehicle from jack stands
3. Start engine and check for exhaust leaks at all flange connections (listen for hissing sounds)
4. Allow engine to reach operating temperature and verify no check engine light illuminates

Verification

• With engine running, inspect all exhaust connections for leaks using soapy water or by feeling for escaping gases
• Verify no unusual exhaust noise or rattling from heat shields
• Check that both oxygen sensor connectors are properly seated and secured
• Confirm check engine light remains off after driving vehicle through several drive cycles
• Verify catalytic converter CARB certification number is visible and matches California requirements

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