2023 GMC Sierra 3500HD Reliability: Tailgate, Injector, Dust and Dually Checks

Start with the exact engine, rear axle and hitch branch

GMC's 2023 matrix keeps the 6.6L Duramax at 445 hp and 910 lb-ft with an Allison ten-speed automatic. The 6.6L gasoline V8 uses a six-speed. Those pairings matter because the injector-connector bulletin is L5P-diesel-specific, while the highest published payload row belongs to a gas DRW configuration.

Record the candidate's engine, transmission, cab, bed, drive, SRW or DRW axle and installed hitch before interpreting either service work or capability. A badge, a brochure maximum and another truck's repair order do not identify the completed vehicle.

The exact 2023 query contains one equipment-specific action

The exact Sierra 3500 model-year query returns 24V060000 / N232426400. It covers certain 2020–2024 HD trucks equipped with power-unlatching tailgates. GM's Part 573 filing further limits the HD branch to the manual gate with power lock and release identified by RPO QT5.

Water can reach the electronic release switch, create a short circuit and allow the gate to unlatch while the truck is in Park. The published interim instruction is to verify that the gate is closed and latched before driving; the remedy replaces the exterior touchpad switch assemblies.

Confirm installed tailgate equipment and VIN status, then retain the itemized repair order. A loose mechanical latch, collision damage, cable problem or different gate configuration should not be relabelled as the same electrical condition without diagnosis. The U.S. query is not Canadian VIN confirmation.

23-NA-027 makes injector replacement a diagnosis, not a shortcut

GM bulletin 23-NA-027 applies to 2017–2023 Sierra 2500HD/3500HD trucks with the L5P diesel. It addresses poor performance, misfires, the malfunction indicator lamp and listed injector-circuit or misfire codes, including P0201–P0208 and P0300–P0308. GM identifies engine-vibration wear between an injector connector terminal and the high-pressure diesel injector as a possible cause.

The procedure requires electrical-connector probing and a visual check for fretting or black powder. Connector replacement is tied to a failed probe or visible finding. The bulletin does not say every misfire is an injector, that every injector needs replacement or that a cleared code proves the circuit was repaired.

For a used diesel, obtain the before-and-after scan, technician findings and parts line. Separate connector repair from injector replacement, fuel-system diagnosis and unrelated combustion or compression work. Do not disturb high-pressure fuel components during a purchase inspection.

23-NA-073 is a severe-dust operating branch

GM bulletin 23-NA-073 includes 2020–2024 Sierra 2500HD/3500HD trucks with all listed engines and transmissions. It applies when severe dusty operation allows dust into the EVAP system, plugging the canister or vent solenoid and setting P0442, P0446, P0455 or P0449.

The published correction is a customer-pay alteration that adds an inline filter. GM describes that filter as a maintenance item to be checked periodically. This is not a universal factory recall, a reason to install parts without the listed operating context or proof that every evaporative code has the same cause.

Ask where the truck worked and whether it regularly followed unpaved roads, construction sites or agricultural equipment. Preserve the code history and technician diagnosis. Inspect hoses, routing, canister and filter work rather than assuming a clean dashboard means the condition never occurred.

Brake-pad percentages remain resettable estimates

The exact 2023 HD owner manual describes front and rear brake-pad-life percentages as estimates. The system is reset after pad replacement and can be reset manually. A high displayed percentage therefore does not replace physical inspection of pads, rotors, sensors and both axles' service records.

The display can also be disabled, including when aftermarket pads without wear sensors are installed. The percentages then disappear while mechanical wear indicators remain. Missing or reset percentages do not diagnose a tailgate, injector or EVAP condition and do not establish pad thickness.

GMC calls for replacing pads as complete axle sets. The manual also distinguishes normal lining-related fluid movement from a hydraulic leak and warns that topping up does not repair a leak. Reconcile the display, invoices and inspection rather than accepting any single signal.

Trailer-brake messages require vehicle-versus-trailer separation

The owner manual distinguishes CHECK TRAILER WIRING from SERVICE TRAILER BRAKE SYSTEM. A wiring message can come from a trailer connection or vehicle-side circuit and requires the manual's separation steps. A persistent service message identifies an integrated trailer-brake-control problem that needs service.

Either message can mean reduced or absent trailer-brake operation. Do not treat acknowledge-and-clear behaviour, a gain display or an unloaded parking-lot check as a repair. Test the intended trailer only under safe conditions and stop if braking response or warning behaviour is abnormal.

Keep trailer connector, trailer wiring, brake magnets or actuators and truck-side controller work as separate line items. The 2023 bulletin set reviewed here does not justify replacing the integrated controller from a message alone.

The 36,000-lb maximum belongs to one diesel DRW row

GMC's 2023 matrix places the 36,000-lb gooseneck maximum on the Duramax Regular Cab long-bed 2WD DRW configuration with the Max Trailering Package. That row has 43,900-lb GCWR, a 20,000-lb conventional rating and a separate 32,000-lb fifth-wheel rating. Hitch methods are not interchangeable.

Other rows are lower. The diesel Crew Cab long-bed 4WD DRW position is 31,180 lb for fifth-wheel and gooseneck use, with a 20,000-lb conventional rating. The highest published payload, 7,442 lb, belongs instead to the gas Regular Cab long-bed 2WD DRW row; it cannot be combined with the Duramax towing maximum.

Brochure ratings are comparison points, not a candidate's VIN-level permission. Verify the certification, payload and trailering labels, installed hitch, passengers, cargo, pin or tongue weight and axle loads. Modifications and options can reduce available capacity.

Verdict and purchase checklist

A supportable 2023 Sierra 3500HD purchase is one whose VIN campaign result, tailgate RPO, gas or diesel powertrain, SRW or DRW branch, brake condition, diagnostic history and work record agree. Obtain build information, current Canadian or U.S. VIN results, itemized invoices and towing or modification history before assigning a condition grade.

On the diesel, compare any misfire or injector-circuit history with the connector findings required by 23-NA-027. On a truck used in dust, compare EVAP codes and filter work with 23-NA-073. On every candidate, inspect the tailgate, brakes, trailer connector, frame, suspension, hitch and labels rather than using a clean scan or completed campaign as a whole-truck verdict.

This guide does not predict remaining life, establish a best or worst year, assign repair prices or certify emissions, towing or Canadian recall status. The commercial link remains a catalogue of disclosed editorial profiles, not live inventory, a verified seller, dealer counts, financing or an offer.