Catalytic Converter - California

Replace the catalytic converters on a 2015-2020 Ford F-150 with 5.0L Coyote V8 engine to meet California emissions standards.

Warnings

Tools required

Parts

• California-compliant catalytic converter assembly (driver side) × 1 — CARB-compliant aftermarket or Ford OEM
• California-compliant catalytic converter assembly (passenger side) × 1 — CARB-compliant aftermarket or Ford OEM
• Exhaust flange gaskets × 4 — Use OEM specification
• Manifold gaskets (if applicable) × 2 — Use OEM specification
• Exhaust hanger isolators × 4 — Replace if damaged

Preparation

1. Ensure engine and exhaust system are completely cold (minimum 1 hour after shutdown)
2. Park vehicle on level surface and engage parking brake
3. Spray all exhaust fasteners with penetrating oil and allow 30+ minutes soak time
4. Raise front of vehicle and support securely on jack stands rated for vehicle weight
5. Disconnect negative battery terminal to prevent O2 sensor fault codes during work
6. Verify replacement catalytic converters have valid CARB Executive Order numbers and match vehicle application

Procedure

1. 1

   Remove heat shields
   Locate and remove the exhaust heat shields covering the catalytic converters. These are typically secured with multiple 10mm bolts. Remove all heat shield bolts and carefully lower shields away from exhaust components. Inspect shields for damage and replace if severely corroded.
   Torque spec

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

   Disconnect upstream oxygen sensors
   Locate the upstream (pre-catalyst) oxygen sensors on both driver and passenger side catalytic converters. Disconnect the electrical connectors by pressing the release tab and pulling apart. Using a 7/8" O2 sensor socket, carefully unthread the sensors from the catalytic converter bungs. Work slowly to avoid damaging sensor threads or bung. If sensors are stuck, apply additional penetrating oil and allow to soak.
   Torque spec

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

   Disconnect downstream oxygen sensors
   Locate the downstream (post-catalyst) oxygen sensors after each catalytic converter. Disconnect electrical connectors and remove sensors using O2 sensor socket. Keep upstream and downstream sensors identified separately to prevent mixing during reinstallation. Inspect sensor condition and replace if more than 100,000 miles or showing damage.
   Torque spec

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

   Disconnect catalytic converter from exhaust manifolds
   Working on the driver side first, locate the two-bolt flange connection between the exhaust manifold and catalytic converter inlet. Use a 15mm socket to remove both flange nuts. Support the catalytic converter weight with one hand or a support jack while removing fasteners. Separate the flange and remove the old gasket. Repeat process on passenger side.
   Torque spec

   Manifold Nuts42 Nm (31 lb-ft)
5. 5

   Disconnect Y-pipe flange connection
   Locate the flange connection where both catalytic converters join at the Y-pipe collector (mid-pipe). This is typically secured with two or three 15mm bolts. Remove all flange bolts while supporting both catalytic converter assemblies. Carefully separate the flange connection and remove the old gasket material.
   Torque spec

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

   Remove exhaust hangers
   Locate the rubber exhaust hangers supporting the catalytic converter assemblies. There are typically 2 hangers per side. Use a pry tool or carefully pull the exhaust pipe studs out of the rubber isolators. Work methodically to avoid tearing the rubber isolators. If isolators are cracked or deteriorated, replace them.
   Torque spec

   Hanger Bolts26 Nm (19 lb-ft)
7. 7

   Remove catalytic converter assemblies
   With all connections and hangers disconnected, carefully lower both catalytic converter assemblies from the vehicle. These components are heavy (approximately 20-30 lbs each) and awkward to maneuver. Work slowly to avoid damaging brake lines, fuel lines, or wiring during removal. Set old converters aside on a protected surface.
   ⚠Catalytic converter assemblies are heavy and awkward. Use proper lifting technique and consider a helper to prevent back injury or component damage.
8. 8

   Clean all flange surfaces
   Use a wire brush or scraper to thoroughly clean all exhaust flange mating surfaces on the manifolds, Y-pipe, and any remaining components. Remove all old gasket material, carbon buildup, and corrosion. Clean surfaces ensure proper sealing and prevent exhaust leaks. Inspect flange surfaces for warping or damage that may prevent proper sealing.
   ℹ️Ensure all gasket residue is completely removed. Even small debris can cause exhaust leaks that trigger check engine lights.
9. 9

   Prepare new catalytic converters
   Unpack new CARB-compliant catalytic converters and verify they match the removed assemblies in terms of mounting points, flange orientation, and oxygen sensor bung locations. Transfer oxygen sensors from old converters if new converters do not include them, or install new sensors. Apply anti-seize compound only to the threads of oxygen sensors, being careful to avoid contaminating the sensor tips.
   ⚠Never apply anti-seize to oxygen sensor tips. Contamination will cause sensor failure and incorrect emissions readings.
   Torque spec

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

    Install new catalytic converter assemblies
    Position the new driver side catalytic converter assembly into place, aligning all mounting points and flanges. Install into rubber exhaust hangers first to support weight. Repeat with passenger side assembly. Do not fully tighten any fasteners yet - only hand-tighten to allow alignment adjustment across all connection points.
    ℹ️Hand-tighten all connections initially to allow proper alignment before final torquing. This prevents binding and ensures leak-free installation.
11. 11

    Install manifold flange connections
    Install new exhaust gaskets at the manifold-to-catalytic converter flanges on both sides. Apply anti-seize compound to the threads of new flange nuts. Install nuts and tighten in a crisscross pattern to ensure even gasket compression. Torque to specification only after all other connections are hand-tight.
    Torque spec

    Manifold Nuts42 Nm (31 lb-ft)
12. 12

    Install Y-pipe flange connection
    Install a new gasket at the Y-pipe collector flange. Apply anti-seize to flange bolt threads. Install all flange bolts and hand-tighten. Once all exhaust connections are hand-tight, begin final torquing sequence starting with this Y-pipe connection, then work toward the manifolds. Use a crisscross pattern when tightening multi-bolt flanges.
    Torque spec

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

    Connect oxygen sensors
    Install all oxygen sensors into their respective bungs, ensuring upstream sensors go to pre-catalyst positions and downstream sensors to post-catalyst positions. Torque sensors to specification using the O2 sensor socket. Reconnect all oxygen sensor electrical connectors, ensuring they click securely into place. Route wiring to avoid contact with hot exhaust components.
    Torque spec

    O2 Sensor45 Nm (33 lb-ft)
14. 14

    Reinstall heat shields
    Position exhaust heat shields back over the catalytic converters and exhaust components. Install all heat shield mounting bolts and torque to specification. Ensure heat shields do not contact the catalytic converters directly and have proper clearance to prevent rattling.
    Torque spec

    Heat Shield Bolts10 Nm (7 lb-ft)
15. 15

    Final inspection and system check
    Reconnect the negative battery terminal. Perform a visual inspection of all connections, ensuring no tools or parts were left in the engine bay. Lower vehicle from jack stands. Start engine and allow to idle for 2-3 minutes while checking for exhaust leaks at all flange connections. Listen for unusual sounds or rattles. Visually inspect for smoke or leaks around all connections.
    ⚠Check engine light may illuminate initially due to O2 sensor adaptation. Light should clear after 1-2 drive cycles if installation is correct.

Reassembly

1. Verify all exhaust connections are torqued to specification using a crisscross pattern on multi-bolt flanges
2. Ensure all oxygen sensor electrical connectors are fully seated and secured
3. Confirm heat shields are properly installed with no contact points that could cause rattles
4. Double-check that no tools, rags, or parts remain in the work area or on the exhaust system

Verification

• Start engine and listen for exhaust leaks at all flange connections - there should be no hissing or ticking sounds
• Verify check engine light is off or clears within 2 drive cycles (oxygen sensor adaptation period)
• Perform a test drive and confirm normal engine performance with no unusual noises from exhaust system
• Check for proper oxygen sensor operation using an OBD-II scanner - all sensors should show switching activity
• Visually inspect all connections after test drive for signs of exhaust soot indicating leaks
• Verify CARB compliance documentation is retained with vehicle records for California smog inspection requirements

Related trouble codes on this vehicle

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