97 Buick Lesabre, had emmisions test done (which it passed) as soon as leaving emmisions test check engine light came on. Any ideas what may have caused this?

It just means it will take longer for the sensor to get up to temp for optimal performance, also check engine light on is a emmisions failure if you in a place that smog tests are required. you will need to replace sensor before test

Hi,
Get the check engine light checked out. Some auto parts stores will check it for free - call first. Otherwise, you'll need a mechanic or the dealer.
GL,
Td

the check engine light covers about 60 different sensors. It could be anything from a loose gas cap to a head gasket. The best way is to have the scan done. Some shops do this free, some charge an hours labor. Personally, I'd go to WalMart and buy one to have. $99. This will tell you everything you need to know. Good luck

No it wont pass, you have a post catalytic 02 sensor this is nicknamed catalytic monitor so it will code up, and you will get a check engine light,drilling a hole the threshold will go below value, so dont do it, Now you can do this take the catalytic out let it soak in water and laundry soap.rinse and install dry.Its worth a try.

Your best bet ,take it to a qualified repair shop that has the proper knowledge an testing equipment .
003 Fuel System Tests Scan Data Tests
003 Engine Peformance Tests Scan Data Tests

Yes it is you need to take that to GM fast!

BEFORE YOU CAN ATTEMP ANY REPAIRS U MUST HAVE THE SYSTEM TESTED FOR THE FAULT CODE THAT IS STORED EACH TIME THE LIGHT IS SET, THERE ARE OVER 50 SUCH FAULTS POSS IN YOUR CAR, SO HAVE THE TEST DONE.

change your lamda probes(seneor)!!!!!!!!

meaning you need to change oil and filter in your car .. or if you have done it recently you need to read your manuel in the glove box and see how to reset this service engine soon light.. Jerry holler if you need more

i believe that either the trnas control module is malfuntioning or you have a sticking valve body in the transmission