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ok im new to california and its smog rules. i have a 2001 chevy silverado and all that is wrong with it is thatits check engine light is on because ny fuel sending unit is bad and is giving me bad readings to my gauge. will that cause me to fail smog even though it has nothing to do with smog???  

in most areas of california...  the smog machines plug directly into the OBD2 port... they talk to the onboard computer... ask if it has performed all of the required internal tests...   some take a week or more of driving to pass... unless you can duplicate the test conditions...

what code do you have????    the fuel sending unit will not set a code.. as far as i know.. but there are various other fuel evaporation system codes that will turn on the check engine light..

without a code... you cannot proceed...  

and anything to do with the fuel system... does have to do with the smog tests here...

the smog police are serious here....  they raided the repair shop across the street from where i used to work... they went in with guns drawn...   took all the mechanics and the shop owner away in hand cuffs..  took their smog machine away on a flat bed... the smog police even have a fleet of modified cars... they drive them into smog shops and watch the techs do their tests...  if they miss something.. that tech gets a huge ticket.. or looses his license..  

Well that will be the first question of the mechanic, in some cases they can try to figure out why the light is on and inform you. But most can't really fix them there because it's against the law for them to touch the car. They are only there to inspect smog and that's it.

One trick is to disconnect the battery all together for 5 minutes and reconnect it again. This will cause the light to go away temporarily. You can go to the smog check then and get it done. However you are still going to need to fix the problem.  
Life.....It's not about how hard you can hit but how hard you can get hit and keep pushing forward, how much you can take and keep pushing forward! - Rocky Balboa

that may or may not work....

get a code reader, some parts stores will read trouble codes for you... some pep boys and auto zones will also...

disconnecting the battery will usually make it refuse to be tested... as the self tests have not been completed...  they will just take your money and tell you to come back in two weeks...

resetting the ecm will also do the same...

resetting the code or disconnecting the battery will also erase the onboard data recorder... that records all the information all the time... and when it sets the trouble code.. it saves that data segment in a file that mechanics can examine with a scan tool that reads live data.. so they know what the car was doing when the code set...

does the Paper work you got from DMV say  TEST ONLY center...  

one more thing.. are you handy around cars and trucks...   code readers start at 40 bucks...    scan tools start at 80 bucks.. and a good one that does a lot is about 140...   look up harbor freight.com      item 98614...   it will also check other friends 96 and newer cars and trucks..  so you might make it pay for its self...  

yeah i am good with the cars and the trucks as far as fixing it and i can do it i just dont have the time right now. i went and got it read and the only thing that was causing it to pop was the fuel sending unit sensor and the sensor in between. (because the fuel sending unit is bad) but all the unit does is go from the tank to my gauge, nothing wrong with the truck, still get the same gas mileage and rides perfect. but it does pop that light. I just dont have the time to drop my gas tank and change it out and i just need the smog test done so i can get base stickers even though it is registered in montana, yay. but with that being the only problem will it pass smog, and i have a code reader but i just got back from iraq and all my stuff is still packed. so i cant give u the actual code number. just what had popped.  

yeah i am good with the cars and the trucks as far as fixing it and i can do it i just dont have the time right now. i went and got it read and the only thing that was causing it to pop was the fuel sending unit sensor and the sensor in between. (because the fuel sending unit is bad) but all the unit does is go from the tank to my gauge, nothing wrong with the truck, still get the same gas mileage and rides perfect. but it does pop that light. I just dont have the time to drop my gas tank and change it out and i just need the smog test done so i can get base stickers even though it is registered in montana, yay. but with that being the only problem will it pass smog, and i have a code reader but i just got back from iraq and all my stuff is still packed. so i cant give u the actual code number. just what had popped.