Hi Scotty.2008 Chevy impala automatic 3.9L 90k miles. codes p0171 and po556. advised by dealer to replace BB sensor and booster . replaced sensor and codes went away for about 60miles-then engine light/codes back on(strange. it was as if reset) should i try to send part back??? Now trying to find out if it is the diaphragm in the booster causing leak. I guess you cant buy that part new--maybe find used good one. Could the cigar smoke test tell if it was that diaphragm part only? A friend says to try started fluid on that diaphragm to see if somethings not right with the pedal depressed-and it would sputter..i like smoke idea better....oh ya-car runs good ! no pedal issue
forgot to mention dealer clamped hose before Booster to determine leak location
Well you can try smoke test but realize that it is a vacuum system so you're better off connecting a hose in a vacuum pump with a gauge and sucking it down and then if the vacuum doesn't stay vacuum and goes to normal air pressure you know the diaphragm is leaking
