Odb port location 1991 buick lesabre

On a 91 Buick you can disconnect the negative battery cable for a minute to clear the codes.

disconect battery wait 5 minutes reconect after 3rd time driveing light will reset itself

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

NO CODES TO SHOW?

blue smoke on startup is generally from worn valve guides or bad stem seals on same (not really terrible as long as it stays the same) It will run rough for a minute 'till the oil in the cylinders is cleared out. Service engine light is pretty much on its own timer and does not mean anything but it's there to annoy you into going to the dealer. If O2 sensor was bad, it would eventually put the red check engine light on.

under the dash you will find a diagnostic port however there are only a few wires going to it,on the top of the port there are two wires side to side take a peace of wire and make a jumper, jump the two wires that are side to side. turn the switch on and count how many times the check engine light blinks it will give you code 12 three times and then the code after that is what is making your car sick. hope this has helped you !

replace the 02 sensor and the light will go off.

I found several shops in my area, Albany, NY that had the older code readers. It worked fine, and cost me $30.00. It showed a bad O2 sensor that I replaced myself. I suggest you go to a reliable shop. Auto Zone/Advance etc.. do not have the right code readers. Joe

Check vacuum tee under hood by fire wall. Looks like a fishing cork, three ports.

You need to have the vehicle scanned or pull the code out with a code reader,and address/fix the code.If you do not repair the problem,you can clear the code,but the service engine light will come right back on.To clear the code,you can disconnect the negative terminal on the battery for at least 20 minutes,then reconnect the battery,but the car is going to be hard to get to idle,because sometimes the computer has to relearn how to idle the engine without stalling.Good luck.