Owners of a 2020-2021 GMC Sierra 2500/3500 equipped with a 6.6L engine may experience a rough idle and reduced engine power. The SES light may be on, with DTC P0123 and P0222 active or in history. This condition may be more noticeable in very cold climates. The condition may be caused by an internal circuit board fault within the throttle body.
Replace the throttle body. Using two 8mm ring terminals and one 8-inch 14-gauge wire, make a good ground wire. Remove the oil fill cap and beauty cover from the left bank rocker cover. Attach one end of the new ground wire to the lower right throttle body fasteners with the crimp side of the ring terminal facing towards the bolt head. Attach the other end of the ground wire to the rocker cover fastener with the crimp side of the ring terminal facing towards he bolt head. Road test to verify the repair.
Attach the other end of the ground wire to the rocker cover fastener.
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Information courtesy of Mitchell 1
Information for Technical Service Bulletins comes from ProDemand, Mitchell 1's auto repair information software for domestic and import vehicles. Headquartered in San Diego, Mitchell 1 has provided quality repair information solutions to the automotive industry since 1918.
Mike Mavrigian
Motor Age Editor
Mike Mavrigian has written thousands of automotive technical magazine articles involving a variety of specialties, from engine building to wheel alignment, and has authored more than a dozen books that crisscross the automotive spectrum. Mike operates Birchwood Automotive, an Ohio shop that builds custom engines and performs vintage vehicle restorations. The shop also features a professional photo studio to document projects and to create images for articles and books.