I have a 1999 Chevy silverado 4x4 5.3 liter that will not pass emissions. It has been taken in 3 times and each reading calls for a drive cycle. How do i complete the drive cycle to pass emissions. The truck has been driven over 400 miles since the first test with several cool down periods. any suggestions

limited info generic answer the cat is usually the last and driving 2 hrs is not going to do it and usually need to do quick drive cycle 2 or 3 times -----or over 125 miles of alternate driving --https://smogcheckvacaville.com/general-motors-drive-cycle-for-smog-check/ ----------- https://repairpal.com/how-to-perform-a-basic-drive-cycle ---------

Drive cycles are the amount of time vehicle has been driven since clear--battery disconnected--Drive vehicle for 1 hour under road conditions--then retest.

Technical problem that needs manufacture.

Take it to autozone or another place like it and have them read the codes and tell us what they are.

It has nothing to do with Miles and EVERYTHING to do with Drive Cycles.. There are certain things that must be tested. Within the first 10 miles, generally speaking you are going to complete the Drive Cycle requirements for ALL the tests except for 2-3. The EVAP/ O2 normally the last ones to get cleared.

Your Vehicle is a 1999 which means that you can pass the I/M test with 2 lights "NOT READY". The EVAP is going to take longer than a few miles, you must fill up your car with fuel above the 3/4 mark and then it has to go below I believe it is 1/2.

But if there are 2 Not Ready's... it will pass

Sometimes the emission light will come on if the gasket on the gas cap is worn or dirty, thus not sealing properly. If it doesn't look worn, then try cleaning it.

Chevy of this model has to be driven 80-100 miles at least to reset the emissions this is if everything is good and all aspects pass and become active this will happen if all is well during the driving cycle each component will start coming on line.Remember to rate my solution this is how i earn my achievements also testimonial Thanks much in advance.

the code you show is for the oxygen sensors post convertor. replace both the o2 sensors after the convertor and the code will go away on its own after a couple normal condition drive cycles

turn key on, now depress the gas pedal 3 times, ......this should reset the light

is there a check engine light? is the turbo running as it should? is it at normal operation temp during test. if pollution control is your cat/ o2 sensor.