2004 cts wont start after adding a clean out smog treatment called mechanic found no codes could it be the evap he thought it was the fuel pump

Try running this through the system. Because you disconnected the battery, you will also have to do a full 'Drive Cycle'.

https://www.duralube.com/collections/fuel-treatments/products/severe-catalytic-exhaust-treatment

https://www.google.com/search?q=emissions+drive+cycle

This is good as well

Dura Lube Severe Fuel System Cleaner- 16 oz.

https://www.duralube.com > products > severe-fuel-syst...

$12.99 $11.99 ... DuraLube Severe Fuel System® Cleaner is highly concentrated and precisely formulated to clean the entire fuel delivery system including Fuel ..

its in the manual read it yet. SM
9 engines used on this car day1, which one, and they are not the same, EVAP = SMOG devices. fuel vents. controlled.
NO DTC error told at all. sad face.

https://eautorepair.net/Marketing/Default.asp


no need to guess, or get wrong answers or guessing
RTM
CTS = cant test sensors? or Caddy tricky story, yes.

I will guess 1 in 9 engines
answer USA only (sorry evap is not the same world wide ,)_
no smog rules are world wide , not yet, next year?


all I see is this, follow the purge tube 15 to the PV1
PV2 is for turbo only car.




or try to buy the part online
then look at it see its looks
then find it on the car from line 15 back.
seems it is in the engine bay next to CAN 3.

go to a better mechanic as he would know that resetting is done with the scan tool

hi solution to evap code it is simple and silly well what it is is fuel evaporation dew to fuel tank cap not sealing or cracked filler pipe this puts the evap code or light on all the best caution it is fuel system you are dealing with

p-1494 is a Leak detection pump switch or mechanical fault within the EVAP system. The possible causes are; An intermittant bad connect in the wiring harness or at the EVAP pump. The EVAP pump is faulty, broken or disconnected vacuum hose within the EVAP system. This code can be very challenging, even to an expert.

SOUND LIKE FUEL PUMP FAILED, CHECK FUEL PUMP FUSE AND RELAY.

I looked up the code and it said p171 was a lean air mixture.
Lucas could help if it were a clogged injector.

Lucas Fuel Treatment
Lucas Fuel Treatment is formulated for both gasoline and diesel engines, carbureted or fuel injected. It gives your fuel system what it really needs - a blend of super slick oils and additives with a high detergent action that allows the engine to operate at maximum efficiency. Also, it cleans and lubricates the carburetor and injectors and causes the fuel to burn more thoroughly for increased power and less fuel consumption. Lucas Fuel Treatment should definitely be used in vehicles that require leaded fuel because it actually replaces the benefits of lead in gasoline without causing harmful emissions. Use it to pass smog tests. Finally, it totally neutralizes the harmful effects of low sulfur diesel fuel.

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I do not know what the humming noise would be, exactly. It's kind of hard to diagnose without hearing what and where.

However, I would check all fluid levels to make sure that they're ok, as a start.

fuel tank cap has to be on for the evap system to operate,engine should always be off while fueling.with cap off it should throw a code for evap system leak.

Hmmm.. Your van has No carburator.. Its direct multiport fuel injection.. It sounds like you have excessive moisture in the tank and lines.. Id try a new fuel filter..

Have you put new sparks plugs in it. If you havent I would try them first. Only run the ac delco plugs listed for the truck. I have had many people come threw the shop with misfiring and trucks running like **** and come to find out they put bosch or ngk plugs in it. Your manual says there good for 100,000 miles but there really only good for about 75,000 or so. Also run some lucas fuel treatment or b12 chemtool. both you ad straight to the gas tank. If it calls for one can for 20 gallons buy two and double the treatment it wont hurt you engine.