Sorry, the NHTSA has not posted this TSB document yet.
You can still get the detailed info from Chevrolet for this TSB. Call your local Chevrolet dealer's service department & ask for a copy of TSB# PIP-4714.
CHEVROLET/GMC: SHUTTLE BUS GENERATOR MODIFICATION P0621. DEALER MAY ENCOUNTER CONCERN OF A SES LIGHT ON WITH DTC P0621 FOUND. MANY CASES THESE VEHICLES ARE USED IN A SHUTTLE BUS APPLICATION. SOME UPFITTERS OF THE SHUTTLE BUSES ARE ORDERING THE VEHICLES WITH DUAL GENERATORS AND REMOVING ONE OF THE GENERATORS TO INSTALL AN ADD ON AIR CONDITIONING COMPRESSOR. *PE
