exhaust

Catalytic Converter - Direct Fit

for 2021 Ford F-150 3.5L V6 EcoBoost · 4WD

Editorial review:Chris Hackleman — Master Technician · 20+ years · Jeff Moore — Master Lexus & Toyota Mechanic · 20+ years

Difficulty

Moderate

Time

1.8 h

Tools

Steps

✓Expert-verified. Personally reviewed and approved by OLP's master technicians (Chris Hackleman & Jeff Moore — 20+ years each). Always follow the vehicle's factory service information and torque specs.

Replace the catalytic converter on a 2021-2024 Ford F-150 3.5L EcoBoost V6 RWD with a direct-fit replacement unit.

Warnings

⚠️Exhaust components remain extremely hot for over an hour after engine shutdown. Allow complete cooling before starting work to prevent severe burns.

⚠Oxygen sensor threads are fragile and easily cross-threaded. Use proper oxygen sensor socket and apply anti-seize only to threads, never to sensor tip.

⚠The EcoBoost engine has two turbochargers and complex exhaust routing. Ensure you are replacing the correct catalytic converter bank for your diagnostic code.

ℹ️Exhaust fasteners on this vehicle are prone to corrosion. Apply penetrating oil 24 hours before work if possible.

Tools required

Vehicle lift or jack stands (rated for truck weight)Essential

Torque wrench (10-60 Nm range)Essential

19mm and 22mm combination wrenchesEssential

Oxygen sensor socket (7/8" or 22mm)Essential

Penetrating oil

Wire brush

Anti-seize compoundEssential

Rust penetrant spray

Socket set (metric)Essential

Exhaust hanger removal tool or pry bar

Parts

Direct-fit catalytic converter assembly × 1 — Use OEM specification or EPA-compliant aftermarket
Exhaust flange gasket set × 1 — Use OEM specification
Oxygen sensor (if damaged or corroded) × 1 — Motorcraft DY1508 or equivalent

Preparation

Park vehicle on level surface and allow exhaust system to cool completely (minimum 2 hours after running)
Raise vehicle on lift or support securely on jack stands rated for truck weight
Spray all exhaust flange bolts, oxygen sensor threads, and hanger bolts with penetrating oil
Disconnect negative battery terminal to prevent oxygen sensor fault codes during removal
Identify which catalytic converter requires replacement (driver side or passenger side bank)
Have fire extinguisher accessible in case of residual fuel or oil ignition from hot components

Procedure

1
Remove heat shields
Locate the heat shield(s) covering the catalytic converter assembly. Remove the heat shield bolts using appropriate socket. The shields may be in multiple sections. Set shields and hardware aside for reinstallation.
Torque spec
Heat Shield Bolts10 Nm (7 lb-ft)
2
Disconnect oxygen sensors
Locate the upstream and downstream oxygen sensors on the catalytic converter. Disconnect the electrical connectors by pressing the release tab. Using the oxygen sensor socket, carefully unthread each sensor from the exhaust housing. Turn counterclockwise slowly to avoid cross-threading or breaking the sensor. If sensors are seized, apply additional penetrating oil and allow to soak before attempting removal.
Torque spec
O2 Sensor45 Nm (33 lb-ft)
3
Disconnect upstream exhaust flange
Locate the flange connection between the turbocharger downpipe and the catalytic converter inlet. Remove the flange bolts (typically 2-3 bolts) using a 19mm wrench or socket. Support the catalytic converter weight with a jack or helper to prevent strain on downstream connections. Separate the flange and remove the old gasket material.
Torque spec
Exhaust Flange Bolts45 Nm (33 lb-ft)
4
Disconnect downstream exhaust flange
Locate the flange connection between the catalytic converter outlet and the intermediate pipe or Y-pipe. Remove the flange bolts using a 19mm or 22mm wrench. The catalytic converter should now be free from hard connections. Remove and discard the old gasket.
Torque spec
Exhaust Flange Bolts45 Nm (33 lb-ft)
5
Release exhaust hangers
Identify the rubber exhaust hangers supporting the catalytic converter assembly (typically 1-2 hangers). Use an exhaust hanger removal tool or pry bar with careful leverage to pop the metal hooks out of the rubber isolators. Have a helper support the catalytic converter weight or use an exhaust jack during this process.
Torque spec
Hanger Bolts23 Nm (17 lb-ft)
6
Remove catalytic converter
With all connections released, carefully lower and remove the catalytic converter assembly from the vehicle. Maneuver around frame rails and crossmembers. The assembly is heavy (approximately 20-30 lbs) and awkward, so use care to avoid dropping or striking other components.
7
Clean mating surfaces
Use a wire brush to thoroughly clean all flange mating surfaces on both the upstream turbocharger connection and downstream intermediate pipe. Remove all old gasket material, carbon buildup, and corrosion. Clean surfaces ensure proper seal and prevent exhaust leaks.
8
Prepare new catalytic converter
Inspect the new catalytic converter for shipping damage and verify all oxygen sensor bungs are present and clear. Install new flange gaskets on both inlet and outlet flanges. Apply a thin coat of anti-seize compound to oxygen sensor threads (threads only, avoiding the sensor tip which must remain clean).
9
Install new catalytic converter
Carefully position the new catalytic converter into place, aligning with upstream and downstream flanges. Engage the exhaust hangers into their rubber isolators. Support the assembly with an exhaust jack or helper while positioning. Verify the assembly sits in its natural position without strain or interference.
Torque spec
Hanger Bolts23 Nm (17 lb-ft)
10
Connect upstream flange
Align the catalytic converter inlet flange with the turbocharger downpipe flange, ensuring the new gasket is properly seated. Install flange bolts with anti-seize compound applied to threads. Tighten bolts in a cross-pattern to the specified torque to ensure even gasket compression and prevent warping.
Torque spec
Exhaust Flange Bolts45 Nm (33 lb-ft)
11
Connect downstream flange
Align the catalytic converter outlet flange with the intermediate pipe flange with new gasket in place. Install flange bolts with anti-seize applied. Tighten in cross-pattern to specified torque. Verify there is no binding or misalignment in the exhaust system.
Torque spec
Exhaust Flange Bolts45 Nm (33 lb-ft)
12
Install oxygen sensors
Thread the oxygen sensors into their bungs by hand first, ensuring they start straight to avoid cross-threading. Tighten using the oxygen sensor socket to specified torque. Do not overtighten as this can damage the sensors. Reconnect the electrical connectors to each oxygen sensor, ensuring they click into place securely.
Torque spec
O2 Sensor45 Nm (33 lb-ft)
13
Reinstall heat shields
Position the heat shield(s) over the catalytic converter assembly. Install and tighten heat shield bolts to specified torque. Ensure shields do not contact any part of the exhaust system where they could rattle or cause interference.
Torque spec
Heat Shield Bolts10 Nm (7 lb-ft)

Reassembly

Reconnect the negative battery terminal
Inspect all connections visually to ensure proper assembly and no tools left in engine bay
Double-check that all oxygen sensor connectors are fully seated and secured

Verification

Start the engine and listen for exhaust leaks at all flange connections and oxygen sensor ports
Allow engine to reach operating temperature and verify no abnormal noises or rattles from exhaust system
Check for exhaust odors in cabin or around vehicle perimeter indicating a leak
Use a scan tool to verify oxygen sensor signals are reading properly and no fault codes are present
Perform a test drive and monitor for check engine light, loss of power, or unusual exhaust sounds
After 50-100 miles of driving, re-inspect all flange bolts for proper torque retention and no loosening