2023 GMC Sierra 2500 HD Service and Repair Manual

This factory service and repair manual for the 2023 GMC Sierra 2500 HD is written for a five-trim range, AT4, Denali, Pro, SLE and SLT, built as a 4-door crew cab pickup, a 4-door extended cab pickup or a 2-door standard cab pickup. Both engines displace 6.6L: a turbocharged diesel V8 of 403 cubic inches and a naturally aspirated gasoline or flex-fuel V8 of 401 cubic inches, both overhead-valve. Its procedures, specifications, torque values, wiring diagrams and diagnostics follow the systems those two engines share and the ones they do not.

Engines covered

• 6.6L V8 (403 cu in) — OHV, turbocharged, diesel
• 6.6L V8 (401 cu in) — OHV, naturally aspirated, gasoline or flex-fuel

Body styles covered

• 4-door crew cab pickup
• 4-door extended cab pickup
• 2-door standard cab pickup

Trims covered

• AT4
• Denali
• Pro
• SLE
• SLT

Known issues on the 2023 Sierra 2500 HD. One recall is on the federal record for this model year, and it concerns trucks with a power-release tailgate: the gate-release switch can short circuit when water gets into it, so the tailgate can unlatch on its own while the truck is parked and then swing open on the road. Owners have logged 31 complaints, and 20 of them, by far the largest group, concern the power train, with a few on tires and the electrical system. Transmission and driveline diagnostics, body wiring diagrams and the latch procedures with their torque values are all documented in this manual.