Visual and functional inspection of emissions control components including oxygen sensors, catalytic converters, EVAP system, and onboard diagnostics to ensure compliance with emissions standards.

Warnings

Tools required

Preparation

1. Ensure vehicle has been driven through complete drive cycle (minimum 50 miles mixed driving)
2. Verify engine is cold to touch before beginning visual inspection
3. Park vehicle on level surface and apply parking brake
4. Gather inspection documentation and state/local emissions requirements

Procedure

1. 1

   Connect OBD-II scanner and retrieve codes
   Locate OBD-II port below driver side dash near steering column. Connect scanner and turn ignition to ON position without starting engine. Retrieve all diagnostic trouble codes (DTCs), freeze frame data, and readiness monitor status. Document any stored, pending, or permanent codes.
2. 2

   Check readiness monitors
   Verify all readiness monitors have completed and are showing 'Ready' status. For 2021-2024 F-150 3.5L EcoBoost, required monitors include: Catalyst, Heated Catalyst, EVAP System, Secondary Air System (if equipped), A/C Refrigerant, Oxygen Sensor, and Oxygen Sensor Heater. Note that one monitor (typically EVAP) may be incomplete and still pass in most jurisdictions.
3. 3

   Inspect fuel cap and EVAP system
   Remove fuel cap and inspect gasket for cracks, tears, or damage. Check cap for proper sealing. Inspect EVAP canister located near rear of vehicle ahead of fuel tank on driver side. Check all vapor hoses for cracks, disconnections, or damage. Verify purge valve connector is secure on engine near intake manifold passenger side.
4. 4

   Inspect catalytic converters
   Visually inspect both catalytic converters from underneath vehicle. The 3.5L EcoBoost has integrated catalytic converters in exhaust manifolds plus downstream cats. Check for physical damage, excessive rust, loose heat shields, or evidence of impact. Listen for rattling when tapping gently with rubber mallet indicating internal substrate failure.
5. 5

   Inspect oxygen sensors
   Locate all four oxygen sensors on the 3.5L EcoBoost (two upstream in turbo exhaust outlets, two downstream after catalytic converters). Verify electrical connectors are secure and free from damage. Check sensor wiring for chafing, burns, or breaks. Sensors should be free from oil contamination or excessive carbon buildup at tips.
6. 6

   Check PCV system and intake
   Inspect PCV valve and hoses in valve cover area. Check air intake system from air filter housing to turbocharger inlets for leaks, cracks in rubber boots, or loose clamps. Verify air filter is clean and properly seated. Inspect turbocharger inlet and outlet connections for oil leaks indicating turbo seal failure.
7. 7

   Inspect exhaust system integrity
   Check entire exhaust system from turbocharger outlets to tailpipe for leaks, holes, or loose connections. Pay special attention to flex pipes near turbos, manifold-to-downpipe connections, and welded joints. Listen for hissing indicating exhaust leaks. Verify all hangers are intact and exhaust is not contacting frame or body.
8. 8

   Check EGR system (if equipped)
   The 3.5L EcoBoost uses cooled EGR. Inspect EGR valve on passenger side of engine near firewall. Check vacuum lines and electrical connector for security. Verify EGR cooler connections are tight and free from coolant leaks. Check for excessive carbon buildup in visible EGR passages.
9. 9

   Verify emission control labels
   Confirm Vehicle Emissions Control Information (VECI) label is present and legible under hood. Verify all emissions equipment listed on label is present and unmodified. Check for any obvious modifications or aftermarket parts affecting emissions system such as tuners, non-compliant exhaust, or intake modifications.
10. 10

    Perform final scan and document results
    Perform final OBD-II scan to confirm no new codes have set during inspection. Document MIL (Malfunction Indicator Lamp) status - should be OFF with engine running. Print or record VIN, odometer reading, readiness monitor status, and any codes found. Clear inspection mode if scanner set it. Complete required emissions inspection documentation per local requirements.

Reassembly

1. Ensure fuel cap is reinstalled and clicked at least 3 times to seal properly
2. Verify all connectors touched during inspection are fully seated and secured
3. Remove scanner from OBD-II port and ensure port cover is reinstalled if equipped

Verification

• Confirm check engine light (MIL) is OFF with engine running
• Verify OBD-II scanner shows 'Ready' status for all required monitors
• Ensure no active or pending DTCs are present in system
• Test drive vehicle briefly to confirm no new codes set and MIL remains off
• Complete emissions inspection certificate or rejection notice per local regulations

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