Chapter 12-4 Emissions Tests Emissions Tests continued OBD Vehicles Exempt from Readiness Checks. Some 1996 and newer vehicles exhibit unique testing characteristics that prevent them from receiving a complete OBD emissions test. These particular vehicles will skip over the readiness checks and go directly to the MIL (Malfunctioning indicator light) check. Check Engine Light. Is the Check Engine light (sometimes labeled as "Service Engine Soon") turned on? When this light is turned on, it indicates that one or more components of your vehicle's emission control system is not working as it was designed to work, and repairs are needed. If the light does not turn on when the OBD system tries to turn it on, this problem must be corrected. Diagnostic Trouble Codes. Why would the OBD system turn on the Check Engine light? These indicators are diagnostic trouble codes that indicate which systems or components are not performing as designed. Reviewing these codes is the first step in diagnosing an emissions-related problem. These codes, along with other information in the OBD system, help guide the emissions repair technicians to faulty parts and take the "guess-work" out of the process. The results are printed on the Vehicle Inspection Report (VIR), which the inspector will give the consumer when the inspection is finished. If the vehicle passes both its OBD emissions test and its safety inspection, it is issued a new sticker. If OBD detects a problem with the vehicle (generally indicated in advance by an illuminated "Check Engine" or "Service Soon" light), the vehicle will fail its inspection and will need to be repaired. 10/08 12:17