Hello Everyone.... I have 01 GMC sierra 4.8.. truck has 150k miles on it.. Runs perfect. Because i dont drive often i unplug the battery for extended periods of time. This caused the same problem with smog that everyone was talking about "2nd air not ready".. I tired the GMC drive cycle at least 15 times nothing would work... What did work was this suggestion :
ADD THIS TO YOUR DRIVICLE, it worked for me. Park next to the the highway or open road and turn the key off. Start the engine, then immediately (while the secondary air pump is still running) get up to 60 MPH and hold for a couple minutes. I saw mine become ready in under a minute.
The secondary air pump runs every time I start my vehicle for 30-60 seconds. I recommend doing this before the engine is up to operating temp to ensure the air pump runs while getting up to speed."
best of luck.. i know this is very frustrating.
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