Check engine light comes on. And then when you try to pass a car it…
Failed smog check, obd2 monitors not ready.
This happens when someone clears the check engine light right before the smog check. The vehicle has to be driven for a while for the system to under go its readiness test. This is referred to as a drive cycle. Some cars require more than one drive cycle on more than one or two days.
What is a Drive Cycle?
A drive cycle is used to replicate certain conditions that are deemed normal for the everyday use of the vehicle. This may include starting the engine and letting it idle for a certain amount of time. Then buckling the seat belt and driving a certain length of time at a certain speed. It may include driving at highway speeds and then slowing down to around 30 mph and then stopping and then returning to 30 mph. Heavy acceleration and soft acceleration. Idling at a stop for 20 seconds.
On many cars, one of these Drive Cycles is sufficient enough to set all or most of the Readiness Monitors. Other vehicles require that this entire process be repeated on two or more successive days.
One reason some vehicles cannot complete the E-Check is the on board diagnostic (OBD II) system readiness monitors are not set. Frequently, this is caused by erasing the memory from the OBD system by either clearing any diagnostic trouble codes (DTC) or disconnecting the battery. If possible, when working on a vehicle that has failed the E-Check OBD II test due to an activated malfunction indicator lamp (MIL, check engine light), do not clear the DTC(s). When the cause of the original failure has been repaired properly, the DTC(s) will clear and the MIL will go out when the OBD system tests the repaired emissions control system.
If the DTC(s) have been cleared, there are various drive cycles to reset the monitors. Some monitors are continuously checked and take little driving to reset those. Some other monitors are checked intermittently and take more specific driving conditions to reset.
Many vehicle manufacturers now include these drive cycles in the vehicle’s owner’s manual. Others will provide information in Technical Service Bulletins (TSB). Please note, some specific published drive cycles are intended to reset all monitors in the shortest amount of time as possible. In many cases, a few days of normal driving, both city and highway, will reset the monitors.