With VCM-A

DEFINITION
Vehicle fails an emission test. Vehicle has excessive "rotten egg" smell. Excessive odors do not necessarily indicate excessive emissions.

PRELIMINARY CHECKS
^ Refer to "Important Preliminary Checks," as described at start of Diagnosis By Symptom. Testing and Inspection
^ Perform "Diagnostic System Check." Testing and Inspection
^ Make sure engine is at normal operating temperature.
^ If EMISSION TEST shows excessive CO and HC check items which cause vehicle to run RICH. Long term fuel trim memory less than 115.
^ If EMISSION TEST shows excessive Nitrogen Oxide (NOx) check items which cause engine to operate LEAN or too hot.
^ Service Bulletins for updates.

SENSORS
Check:
^ If the scan tool indicates a very high coolant temperature and the system is running LEAN: check the cooling system and cooling fan for proper operation.

FUEL SYSTEM
Check:
^ If the system is running rich, (long term fuel trim less than 115).
If the system is running lean, (long term fuel trim greater than 150).
^ For properly installed fuel cap.
^ Fuel pressure. Refer to "Chart A-6". Related Tests, Information and Procedures
^ Canister for fuel loading.
^ Injector balance test. Refer to "Chart A-7" of appropriate engine VIN. Related Tests, Information and Procedures

IGNITION SYSTEM
Check:
^ Ignition system, incorrect timing, or excessive advance.
^ Spark plugs, plug wires, and ignition components.

ADDITIONAL CHECKS
Check:
^ For vacuum leaks.
^ For lead contamination of catalytic converter (look for the removal of fuel filler neck restrictor).
^ Carbon buildup. Remove carbon with top engine cleaner. Follow instructions on can.
^ EGR valve for not opening.
^ Crankcase ventilation valve for being plugged, stuck or blocked crankcase ventilation hose.