Q: Auto Zone BB2 Diagnostic on 2001 Chevrolet Astro

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The van, after fuel fill up, has to be started twice. Service engine light is on and two diagnostic tests at auto zone gave 2 codes BB1 and BB2. The common diagnosis of the 2 tests was failed or defective ftp (fuel tank pressure) sensor. The other diagnosis were failed canister purge valve, and check connector, wiring, loose hoses and fittings. Where is the FTP sensor located? On the top of fuel tank? And where is the canister purge valve located?
Thaks, Phil
(1) Answer
(1) Comments
The codes that you were given by Auto Zone are not in the correct format. they should be PXXXX as in P and then 4 numbers. I feel that Auto Zone misleads people because they don't really know how to trace the codes or even what they actually mean. The Fuel Tank Pressure Sensor will not effect the performance of the vehicle. it is for the EVAP testing only. it is located on top of the fuel pump module.The Canister Purge Valve would almost never effect performance either unless it was completely smashed which would cause a vacuum leak. Do you 'top off' your tank when you fill up? This can cause lots of problems because you can flood your engine with gasoline. it can also damage these EVAP sensors and saturate your carbon canister, none of which is good or cheap to repair.
Is it best to not ever top of the fuel tank?But rather stop fueling before attempting to top off the tank,for checking mileage or whatever?? What product do you service mostly??