For some people, they can get the required number of drive cycle in as little as 50 miles while others may drive a few hundred before getting the drive cycles conditions met.

15 minutes of steady driving on an expressway/highway followed by 20 minutes of stop-and-go driving with at least four 30-second idle periods. Allow the vehicle to sit for at least eight hours without starting the engine. Then, start the engine and complete the above driving cycle.

The PCM can perform this test once during the drive cycle. As I discussed earlier, most emissions-related DTCs take at least two drive cycles to set, so it stands to reason it will take at least two passes to turn off the MIL. Keep in mind the second drive cycle will not be complete until you turn off the ignition.

It involves a special test drive that duplicates the scenario of a person starting the car and making a short freeway trip, as if driving to work. While the drive cycle test is going, the engine computer runs a series of tests or “readiness monitors” to see if the emissions system is working properly.

Here’s something you probably don’t know: after clearing the car’s computer you will need to drive for about 50 to 100 miles. As you drive your car the computer will monitor all the sensors and register the results. You can use GOFAR to constantly monitor your car diagnostics.

If you clear the ‘Check Engine’ light, or reset the OBD-II monitors right before your emissions test, your vehicle typically will not pass because the catalyst and EVAP monitors need time to run. If it’s not in a “ready” state, your vehicle will automatically fail.

If you are sure that you have fixed the problem causing the check engine light, the engine light will reset itself after 10-20 successful cycles, and as you can imagine – 10-20 successful cycles can take a lot of time. Therefore it’s much easier to reset the check engine light with an OBD2 scanner.

Permanent codes are a special type introduced more recently which can not be cleared using a scan tool. If you have a permanent code the vehicle will clear it itself once the cause has been addressed and sufficient data has been gathered by driving under different conditions (idling, stop and go, highway)

When should DTCs be cleared? After the repair has been verified. A type ________ DTC is set if an emission problem may cause damage to the catalytic converter.

Registered. From what I remember, clearing the error codes especially with a MAF fault does indeed have a positive impact on how the engine management system works due toi the fact that a maf error code makes the engine run on built-in tables, ignoring input from the MAF sensor as a failsafe.

The ‘Clear all DTC’ button doesn’t work….

1. Remove Neg – off battery for 3 minutes.
2. Leave drivers door open and reconnect battery.
3. Leave bonnet open and switch car ignition lights on ( ANOTHER 3 MINUTES) DO NOT START THE CAR.

It’s called fraudulent concealment and it is illegal. Many states will allow punitive damages. This car dealership should count themselves lucky that you discovered this problem before it caused any personal injuries.