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dashboard message reads, service brake booster. on 2004 Chevrolet Silverado 1500
We had one of these recently, and it turned out to be an electrical problem. I don't remember the details, but I believe it was a corroded connector at the ABS Module causing the problems. If your brakes are actually feeling ok, with no dropping or hard brake pedal, the problem is likely electrical rather than mechanical (meaning, the booster itself is ok). May wish to consider getting a professional on this one, depending on your skill level.
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Have scan test on brake system performed.
If auto savvy, check vacuum hose and check valve at booster. Do brakes feel ok