Catalytic Converter - Universal

This procedure covers the removal and replacement of a universal catalytic converter on a 2015-2020 Ford F-150 with the 3.5L EcoBoost V6 engine, including exhaust system disassembly, oxygen sensor handling, and proper reassembly with torque specifications.

Warnings

Tools required

Parts

• Universal catalytic converter (CARB or EPA compliant as required) × 1 — Match pipe diameter and catalytic converter size to factory specs
• Exhaust flange gaskets × 2 — Use OEM specification
• Exhaust clamps (if using universal slip-fit converter) × 2 — Match exhaust pipe diameter
• Exhaust flange bolts/nuts × 8 — M10 or M12 grade 8.8 or higher
• Heat shield (if replacing) × 1 — Use OEM specification if damaged

Preparation

1. Park vehicle on level ground and apply parking brake. Place wheel chocks behind rear wheels.
2. Allow exhaust system to cool completely (minimum 2 hours after engine operation).
3. If available, clear diagnostic trouble codes and note which oxygen sensor/catalytic converter is flagged (Bank 1 or Bank 2).
4. Raise vehicle using floor jack and support securely on jack stands at manufacturer-recommended lift points. Verify stability before working underneath.
5. Apply penetrating oil to all exhaust flange bolts, oxygen sensor threads, hanger bolts, and heat shield bolts. Allow 15-30 minutes to penetrate.
6. Locate the catalytic converter to be replaced. Bank 1 is passenger side, Bank 2 is driver side on the 3.5L EcoBoost.

Procedure

1. 1

   Disconnect oxygen sensors
   Locate the upstream (pre-cat) and downstream (post-cat) oxygen sensors on the catalytic converter being replaced. Disconnect the electrical connectors by pressing the release tab and pulling apart. Using an oxygen sensor socket or 22mm wrench, carefully remove both oxygen sensors by turning counterclockwise. Inspect sensor threads and replace sensors if damaged or contaminated.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
2. 2

   Remove heat shields
   Remove the heat shield bolts securing the catalytic converter heat shield using appropriate socket. The 3.5L EcoBoost has heat shields covering the converters to protect underbody components. Remove shields carefully and inspect for damage. Set aside for reinstallation or replacement.
   Torque spec

   Heat Shield Bolts10 Nm (7 lb-ft)
3. 3

   Support exhaust system
   Use a jack stand or exhaust support stand to support the exhaust system downstream of the catalytic converter. This prevents the exhaust from dropping and damaging hangers or other components when the converter is removed.
   ⚠Ensure exhaust support is stable and will not shift during cutting or removal operations.
4. 4

   Disconnect upstream exhaust flange
   Locate the exhaust flange connecting the turbocharger downpipe to the catalytic converter inlet. Remove the flange bolts using appropriate socket. The flange may be seized due to heat and corrosion. Apply additional penetrating oil if necessary and use a breaker bar for leverage. Separate the flange connection and remove 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 and mid-pipe section. Use an exhaust hanger removal tool or carefully pry the hangers off their mounting points using a pry bar. Note the orientation and position of hangers for reinstallation.
   ⚠Rubber exhaust hangers can tear if overstretched. Apply lubricant and use steady pressure to remove.
   Torque spec

   Hanger Bolts23 Nm (17 lb-ft)
6. 6

   Mark and cut exhaust pipe (universal converter)
   Measure the length of the factory catalytic converter from inlet flange to the point where it connects to the mid-pipe. Mark the mid-pipe approximately 2-3 inches downstream of the factory weld joint to allow sufficient pipe length for the universal converter slip-fit connection. Use a reciprocating saw with bi-metal blade or pipe cutter to make a clean, straight cut through the exhaust pipe at the marked location. Deburr the cut edge with a file.
   ⚠️Wear safety glasses and gloves when cutting exhaust pipe. Metal shavings and sparks can cause injury.
   ℹ️Ensure cut is square and straight to allow proper sealing with universal converter clamps or welds.
7. 7

   Remove catalytic converter
   With the upstream flange disconnected and downstream pipe cut, carefully lower and remove the failed catalytic converter from the vehicle. Inspect the mounting points and surrounding components for damage. Clean the turbocharger downpipe flange surface using a wire brush to remove old gasket material and carbon buildup.
   ⚠Catalytic converter contains precious metals and should be properly recycled. Do not dispose of in regular trash.
8. 8

   Prepare universal catalytic converter
   Compare the universal catalytic converter dimensions to the factory unit to ensure proper fit. The converter should have similar length and pipe diameter. If the universal converter requires adapter pipes or reducers, assemble them according to manufacturer instructions. Test-fit the universal converter to verify alignment with the turbocharger downpipe flange and the cut mid-pipe before final installation.
   ℹ️Universal converters may have directional flow arrows. Ensure the flow direction matches exhaust flow from engine to tailpipe.
9. 9

   Install universal catalytic converter inlet
   Apply anti-seize compound to new exhaust flange bolt threads. Position a new exhaust flange gasket between the turbocharger downpipe and the catalytic converter inlet flange. Align the universal converter inlet with the downpipe flange and hand-thread all flange bolts. Torque the flange bolts in a crisscross pattern to specification to ensure even gasket compression and seal.
   Torque spec

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

    Connect catalytic converter outlet
    Slide the outlet end of the universal catalytic converter over the cut mid-pipe (or vice versa depending on converter design). Ensure at least 2 inches of overlap for proper seal. Position exhaust clamps over the slip-fit joint but do not fully tighten yet. Adjust the converter position to align with exhaust hangers and ensure proper clearance from underbody components, fuel lines, and brake lines.
    ⚠Maintain minimum 1 inch clearance between catalytic converter and all heat-sensitive components including fuel lines, brake lines, wiring, and body panels.
11. 11

    Reinstall exhaust hangers
    Reconnect the rubber exhaust hangers to their mounting points, ensuring the exhaust system is properly supported and aligned. The system should hang naturally without binding or stress points. If hanger bolts were removed, torque them to specification.
    Torque spec

    Hanger Bolts23 Nm (17 lb-ft)
12. 12

    Tighten slip-fit connections
    With the exhaust system properly aligned and supported, tighten the slip-fit exhaust clamps on the universal catalytic converter outlet according to clamp manufacturer specifications (typically 40-50 Nm). Ensure clamps are positioned to cover the full overlap area and are tightened evenly.
    ℹ️If welding the universal converter instead of clamping, ensure adequate ventilation and follow proper welding safety procedures.
13. 13

    Install oxygen sensors
    Apply a thin coat of anti-seize compound to the oxygen sensor threads only, being extremely careful not to contaminate the sensor tip or element. Thread both oxygen sensors (upstream and downstream) into the new catalytic converter by hand until finger-tight. Use oxygen sensor socket to tighten sensors to specification. Reconnect the electrical connectors to both sensors, ensuring they click securely into place.
    ⚠Do not over-torque oxygen sensors as this can damage the threads in the catalytic converter. Never apply anti-seize to the sensor element or tip.
    Torque spec

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

    Reinstall heat shields
    Position the heat shields over the catalytic converter in their original locations. Install and torque heat shield bolts to specification. Ensure heat shields are not contacting the catalytic converter body and have proper clearance.
    Torque spec

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

    Final inspection and system check
    Perform a thorough visual inspection of all connections, ensuring all fasteners are tight and properly torqued. Verify proper clearance around the catalytic converter and exhaust system. Remove jack stands and lower vehicle to the ground. Start the engine and allow it to idle while listening for exhaust leaks at all connection points. Check for unusual vibrations or rattles. Allow engine to reach operating temperature and verify no leaks are present.
    ⚠Exhaust leaks may not be immediately apparent when cold. Re-check all connections after engine reaches full operating temperature.

Reassembly

1. Torque all fasteners to specifications using a calibrated torque wrench in the sequence specified.
2. Verify all oxygen sensor electrical connectors are fully seated and secured.
3. Ensure heat shields are properly installed and not contacting the catalytic converter body.
4. Confirm minimum 1 inch clearance exists between exhaust components and all heat-sensitive parts.
5. If welding was performed, inspect welds for completeness and penetration.

Verification

• Start engine and verify no exhaust leaks are present at flange connections or slip-fit joints.
• Allow engine to reach full operating temperature and re-inspect all connections for leaks.
• Use OBD-II scanner to clear any existing diagnostic trouble codes related to the catalytic converter or oxygen sensors.
• Test drive vehicle for 15-20 minutes under varied driving conditions to allow oxygen sensors to cycle and verify proper catalytic converter function.
• After test drive, scan for diagnostic trouble codes. The system may require 1-2 drive cycles before readiness monitors complete.
• Perform a final visual inspection under the vehicle to verify no exhaust leaks, proper clearances maintained, and all components secure.
• Monitor oxygen sensor data using scan tool to verify upstream and downstream sensors are reading appropriately and catalytic converter is functioning (downstream sensor should show reduced fluctuation compared to upstream).

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