Failed CA smog test due to coputer reset

Smog test guy asked me whether i had disconnected battery recently. The day before i had battery disconnected and recharged while having oil changed and serviced. Car has 50,000 miles and is in flawless shape- always serviced and use best synthetic oil and premium gas. he said computer need to reset itself since i only drove it since recharge. I trust smog guy - have used him for 15 years; he told i need drive on freeway for 25 miles before taking it in so it resets. I only drive it 5 to 10 miles per week. Is there any other way to reset computer sensors other than driving. I know very little about engines. I baby car, keep it serviced and drive it twice a week in SF, CA. He actually wants to buy it from me. What happens when battery is disconnected? Will driving reset it? If so how much should I drive?

You’ll need to pull out of your normal routine and get this car out for a good drive for a couple of days to get the emissions data restored. 5 to 10 miles a week will not get the job done. Take the car for a weekend road trip and see some sights. Plan on driving across the Golden Gate, then tour a bit of downtown. That should do it.

The ECM (engine control module or computer) checks it’s own emissions on all 1996 and newer cars by Federal law. When you disconnected the battery, the computer lost all of it’s stored data. The emissions protocols require a certain amount of stored data to determine the emissions condition of the car. This is known as ‘emissions ready’.

Your car is now not ‘emissions ready’, and must be driven a certain way for a certain number of miles to recollect the required data. I found with most cars that a couple of days of mixed driving, like a bit of highway and a bit of street (stop-n-go) driving will do the trick. I had one friend with a Nissan that managed to get ‘emissions ready’ in a single day just by taking in the sights around here in Atlanta, about 20 miles of driving.

Thank you. I wanted to confirm what I was told by my smog guy; who I have used for 15 years and trust. He actually wants to buy my car because it is in good shape. His english is not so easy to understand and he was busy - so I wanted to confirm his information. Oh and crap - I thought I was being good to my car by servicing it and getting the battery charged up to capacity before smogging it. All I really needed was an oil change; so, I done myself in. Time to take a long drive. Luckily my registration isn’t due for 8 weeks.

Thanks again. Your response confirms what I was told and thus I don’t need to embarrass myself with my mechanic because there are no “short cuts” - I need to drive it to collect data.

Yes sir that is PRECISELY what you need to do. I havent seen many cars that need to be driven more than 1-2 hours however to get all the emissions ECU tests completed. All you need to do is drive to get some data logged in your ECU.

Thank you. I use the car a three of days a week for round trips downtown San Francisco which is in total a 5 mile round trip. So I need head out for a couple of 1/2 hour drives - maybe lunch on the Half moon Bay. Thanks for backing up the advice. I feel less freaked. Damn, I thought I was too clever by half for getting the battery completely charged while service; but I done myself in.

oops! keyboard malfunction due to faulty 2 finger typing = COMPUTER reset