Emissions Inspection

This procedure covers the emissions inspection process for a 2015-2020 Ford F-150 with 5.0L Coyote V8, including visual inspection of emissions components, diagnostic scan, and functional testing of the evaporative emissions system and catalytic converters.

Warnings

Tools required

Parts

• Gas cap (if damaged or missing seal) × 1 — Use OEM Ford fuel cap

Preparation

1. Ensure vehicle has been driven through a complete drive cycle and engine is at normal operating temperature before beginning inspection
2. Park vehicle on level surface and engage parking brake
3. Allow exhaust system to cool for at least 30 minutes if vehicle was recently operated
4. Verify that Check Engine Light (MIL) is not illuminated on instrument cluster
5. Have vehicle registration and previous inspection records available for reference

Procedure

1. 1

   Perform OBD-II diagnostic scan
   Connect OBD-II scan tool to the diagnostic port located under the driver side dashboard. Turn ignition to ON position without starting engine. Retrieve any stored diagnostic trouble codes (DTCs) and check emissions readiness monitor status. For 2015-2020 F-150 5.0L V8, all monitors except EVAP and O2 sensor heater must be in READY status. Record any pending or confirmed codes.
2. 2

   Inspect fuel cap and filler neck
   Remove fuel cap and inspect the rubber seal for cracks, deterioration, or damage. Check that cap clicks at least three times when tightened. Inspect fuel filler neck for corrosion, damage, or fuel stains indicating leaks. Verify cap tether is intact and secure. Replace fuel cap if seal is compromised or cap does not seal properly.
3. 3

   Visual inspection of engine bay emissions components
   Open hood and visually inspect all accessible emissions components. Check air intake system from air filter box to throttle body for cracks, disconnected hoses, or loose clamps. Inspect PCV valve hose connections and crankcase ventilation system for proper routing. Verify all vacuum lines are connected and free from cracks. Check that engine oil cap is present and sealing properly. Inspect EVAP canister purge valve (mounted on driver side of engine) and its electrical connector for damage.
4. 4

   Inspect exhaust system from underneath
   Raise vehicle on lift or support safely on jack stands. Perform complete visual inspection of exhaust system from manifolds to tailpipe. Inspect all four catalytic converters (two primary cats close to manifolds, two secondary cats further downstream) for physical damage, signs of overheating, or missing heat shields. Check for exhaust leaks at manifold flanges, pipe connections, and welds. Inspect all oxygen sensors (four total: two upstream, two downstream) for physical damage and secure electrical connections. Look for any missing or damaged exhaust hangers.
5. 5

   Inspect EVAP system components
   Locate and inspect the EVAP canister mounted ahead of the spare tire area on driver side frame rail. Check canister for physical damage, corrosion, or signs of fuel saturation. Inspect EVAP lines running from fuel tank to canister and from canister to engine bay for damage, kinks, or disconnections. Verify canister vent valve (mounted on canister) is secure and connector is intact. Check fuel tank for damage or signs of leakage.
6. 6

   Test EVAP system functionality
   Using scan tool, perform EVAP system leak test if capability exists. Monitor fuel tank pressure sensor readings with engine running and purge valve commanded open. Pressure should decrease indicating proper purge function. If smoke machine is available, perform smoke test on EVAP system to identify any leaks. Common leak points include purge valve, vent valve, fuel cap seal, and EVAP line connections.
7. 7

   Inspect oxygen sensors and wiring
   While underneath vehicle, closely inspect all four oxygen sensor connectors for corrosion, damage, or oil contamination. Trace sensor wiring back to ensure no chafing against exhaust components or frame. Check sensor bodies for carbon buildup or physical damage. Verify all sensors are tight in their bungs. Use scan tool to monitor all oxygen sensor signals with engine at idle - upstream sensors should show fluctuating voltage between 0.1-0.9V, downstream sensors should be relatively stable around 0.5V indicating catalytic converter efficiency.
8. 8

   Check for exhaust system leaks under operation
   With vehicle still raised, have assistant start engine and bring to idle. Listen carefully for any exhaust leaks at manifold gaskets, pipe connections, and flex joints. Pay special attention to areas around catalytic converters and oxygen sensors. Small leaks before oxygen sensors can cause false lean readings and set emissions codes. Use soapy water spray on suspected leak areas if necessary.
9. 9

   Verify catalyst efficiency with scan tool
   With engine at normal operating temperature and idling, use scan tool to monitor upstream and downstream oxygen sensor voltages. Calculate switching ratio between upstream and downstream sensors for each bank. Healthy catalytic converters should show minimal switching activity on downstream sensors compared to upstream (typically less than 20% activity). Excessive downstream sensor activity indicates deteriorated catalyst efficiency.
10. 10

    Document inspection results
    Lower vehicle and turn off engine. Document all findings including DTC codes retrieved, monitor readiness status, condition of all inspected components, and results of functional tests. Note any components requiring replacement or repair. Clear any soft codes only if repairs have been completed and verified. Print or record freeze frame data if any DTCs are present for diagnostic reference.

Reassembly

1. Ensure fuel cap is reinstalled and clicks at least three times
2. Verify all hood latches are secure after closing hood
3. If any components were removed for inspection, ensure all connectors are fully seated and clips engaged

Verification

• Confirm no diagnostic trouble codes are present and Check Engine Light (MIL) is not illuminated
• Verify all required emissions monitors show READY status on scan tool
• Confirm no exhaust leaks are audible with engine running
• Test drive vehicle to ensure proper operation and verify MIL does not illuminate
• For jurisdictions with dyno testing, vehicle must meet specified emissions limits during loaded test

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