Visual and functional inspection of emissions control components to verify proper operation and compliance with environmental regulations.

Warnings

Tools required

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine to cool completely if recently operated
3. Locate OBD-II diagnostic port under driver side dashboard
4. Ensure fuel cap is present and properly sealed

Procedure

1. 1

   Scan for diagnostic trouble codes
   Connect OBD-II scanner to diagnostic port. Turn ignition to ON position without starting engine. Retrieve any stored diagnostic trouble codes (DTCs) and freeze frame data. Record all codes, particularly P0420/P0430 (catalyst efficiency) and P0440-P0457 (EVAP system codes). Check that all emissions monitors show 'Ready' status.
2. 2

   Inspect malfunction indicator lamp
   Turn ignition to ON position and verify Check Engine Light (MIL) illuminates during bulb check, then extinguishes after engine start. MIL must function properly and should not be illuminated during normal operation. If MIL remains on, address DTCs before proceeding.
3. 3

   Inspect fuel cap and seal
   Remove fuel cap and inspect gasket for cracks, deterioration, or damage. Check cap for proper ratcheting action when tightened. Inspect filler neck for damage. A faulty cap is the most common cause of P0442 (small EVAP leak) codes. Replace if gasket is compromised or ratchet mechanism fails.
4. 4

   Inspect air intake system
   Visually inspect air filter housing for proper seating and secure closure. Check intake duct from air box to throttle body for cracks, disconnections, or loose clamps. Any unmetered air entering after the MAF sensor will cause lean condition codes and emissions failures.
5. 5

   Inspect EVAP system components
   Locate charcoal canister under vehicle near fuel tank (driver side rear). Inspect canister for physical damage or saturation. Check visible vapor lines for cracks, kinks, or disconnections. Inspect purge valve solenoid on engine (left side near firewall) for secure electrical connection and mounting.
6. 6

   Inspect exhaust system integrity
   Visually inspect exhaust system from manifold to tailpipe for leaks, damage, or excessive corrosion. Pay special attention to manifold-to-catalytic converter connection and flex pipe section. Listen for hissing or ticking sounds indicating exhaust leaks. Any pre-catalyst leaks will affect oxygen sensor readings and cause emissions failures.
   ⚠Exhaust components may be extremely hot - ensure system is completely cool
7. 7

   Inspect catalytic converter
   Inspect catalytic converter housing for physical damage, dents, or heat discoloration indicating internal failure. Check for rattling sounds when tapping converter gently - internal substrate breakup indicates replacement needed. Verify heat shields are present and secure.
8. 8

   Inspect oxygen sensors
   Locate upstream oxygen sensor (Bank 1 Sensor 1) in exhaust manifold and downstream sensor after catalytic converter. Check electrical connectors for corrosion or damage. Verify sensors are not physically damaged and wiring is secure. Check for oil contamination on sensor tips indicating potential engine issues.
9. 9

   Inspect PCV system
   Locate PCV valve in valve cover (right side, near firewall). Check vacuum hose connections to PCV valve and intake manifold. Shake PCV valve to verify rattle - lack of rattle indicates stuck/failed valve. Inspect hoses for cracks or deterioration. Failed PCV causes increased crankcase pressure and oil consumption.
10. 10

    Document inspection results
    Record all findings including DTC codes, monitor readiness status, and physical condition of all emissions components. Note any components requiring replacement or further diagnosis. Clear any pending codes only after repairs are completed. For state inspections, print readiness monitor report showing all systems ready.

Reassembly

1. Ensure all inspected components are reconnected and secured properly
2. Verify fuel cap is reinstalled and clicks at least 3 times when tightened
3. Disconnect OBD-II scanner and ensure diagnostic port cover is replaced if equipped

Verification

• Start engine and verify Check Engine Light extinguishes after 3-5 seconds
• Confirm no new diagnostic trouble codes are present after inspection
• Verify all emissions monitor systems show 'Ready' status on OBD-II scanner
• Ensure no abnormal exhaust smoke or odors are present during idle

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