2023 GMC Sierra powertrain problems

Engine suddenly seizes or shuts down without warning during highway driving, leaving the truck stranded in traffic. Owners report the vehicle goes into neutral electronically and loses all power. Multiple incidents occur after recall remedy (oil change) was completed. In some cases, vehicles had passed recall inspection only days or weeks before catastrophic failure.

When: Various mileage: 20k–41k miles; within 48 hours to 6 months post-recall remedy in several cases; at highway speeds (55–75 mph)

Symptoms owners cite: Complete loss of engine power while driving; Engine goes into neutral electronically; Engine will not restart; Loud whining noise from transmission locked in gear; Ticking noise before shutdown; No oil in engine (internal consumption); Lifter chatter preceding failure; No warning lights before failure in most cases

Codes mentioned: Camshaft position sensor / cam-crank correlation error (exact code not captured in some reports), P0700 (Engine Control Module), Low oil pressure warning

Repairs/costs cited: Full engine replacement required; parts on national back order with wait times of 4–12 weeks or longer. Tow costs $175–paid out-of-pocket in at least one case. New engines installed; one failed again days later.

Recalls/TSBs owners mention: Recall 25V-274 (L87 6.2L V8 engine) directs oil change to 0W-40 viscosity and oil cap replacement. Recall inspection protocol includes PicoScope diagnostic test, claimed to 'pass' vehicles that later suffered catastrophic failure. No internal component replacement or crankshaft/rod inspection occurs under recall remedy. GMC warranty honored for engine replacement in cases where failure confirmed; GMC customer assistance opened case numbers; some owners denied vehicle replacement or refund requests.

Transmission makes violent downshifts with loud clanking or slamming noises, jolting the vehicle forward abruptly. Most common in 10-speed transmissions; occurs after vehicle is warm (30–60 minutes of driving). Downshift jerking requires extra braking force and can startle driver, creating safety risk when stopping.

When: Typically after warm-up at 11k–35k miles; occurs during deceleration, downshifting from 2nd to 1st gear, and at lower speeds (25–55 mph)

Symptoms owners cite: Violent downshift with hard clunk or slamming noise; Rough jolt forward on downshift; Vehicle shudders abnormally during shifts; Transmission feels strained; Rattling at low RPMs during upshift; No warning lights in most instances

Codes mentioned: P0747 (Transmission Control Module – solenoid issue)

Repairs/costs cited: Dealers replace valve body; some also perform transmission fluid and filter changes. Repair may require transmission fluid flush. In at least one case, rebuilt transmission also installed after internal defects found (metal shavings). Valve body parts on national back order; wait times 3–12 weeks reported. One owner used AAMCO to source used transmission unit when new parts unavailable.

Recalls/TSBs owners mention: Valve body replacement covered under warranty. Dealers unable to replicate intermittent issues during short test drives; some owners requested extended test drives or brought video evidence. Extended warranty (10 years / 150k miles) denied to at least one owner. GM aware of defects; case numbers opened.

Rear wheels briefly lock up during acceleration or downshifting, causing tires to squeal and vehicle to slide. Vehicle enters limp mode, restricting speed to 30–40 mph or trapping in single gear (often 5th or 1st). Occurs unpredictably, sometimes while towing or using cruise control, sometimes not. Hazardous in wet or snowy conditions and high-speed interstate driving.

When: At 12k–65k miles; during downshifting, acceleration, and towing; at speeds 25–70 mph

Symptoms owners cite: Brief rear axle/wheel lock-up lasting 1–2 seconds; Tires squeal loudly; Vehicle slide or loss of directional control; Transmission enters limp mode; Speed reduced to 30–40 mph; Unable to shift past 5th gear (in some cases); Check engine light and transmission warning lights illuminate (sometimes delayed); Multiple trouble codes generated (20+ in one report)

Codes mentioned: P0747 (Transmission solenoid), P0700 (Engine Control Module general transmission fault), U0073 (Transmission Control Module communication error)

Repairs/costs cited: Valve body replacement cited as fix; some dealers also reference spacer plate, check balls replacement. Parts back order 3–12 weeks. In one case, dealer blamed adaptive cruise during towing; owner found no manual prohibition. One truck locked up 4 times during 225-mile tow trip; dealer found no stored codes and blamed cruise control use.

Recalls/TSBs owners mention: Dealers confirm valve body defect; some reference known issue across 2020–2024 model years. Recall likely applicable but not explicitly cited in all narratives. GMC dealer claims no codes stored during incidents; blamed cruise control rather than transmission defect. Extended warranty questioned by at least one owner.

Vehicle suddenly loses acceleration power while driving, limiting speed to 40 mph or less. Dash displays 'reduced acceleration' or 'service traction control' warnings. Condition occurs intermittently, sometimes without warning, making it unpredictable and dangerous when merging or passing. Multiple dealership visits fail to permanently resolve.

When: Multiple occurrences; one case recurring over months; at highway speeds 40–70 mph; intermittent onset

Symptoms owners cite: Sudden loss of acceleration response; Speed capped at 40 mph; Dash warns 'reduced acceleration' and 'service ESC' / 'service traction control'; Loss of power steering capability; Difficult to turn wheel and apply brakes; Intermittent and unpredictable occurrence; RPMs spike when attempting to accelerate; Some warning messages appear; condition also occurs without warning

Codes mentioned: P0700 (general transmission/engine fault)

Repairs/costs cited: Valve body replacement, corrosion cleaning on ground wires, and TCM software update attempted; multiple visits required. One case: 30+ cumulative days out of service with multiple repair attempts; condition recurred. Another case: owner almost hit by semi while unable to accelerate in traffic. Owner described as unsafe for daily operation.

Recalls/TSBs owners mention: GMC dealer and manufacturer aware; case numbers opened. Dealers attempted fixes without permanent resolution. Owner advised to contact dealer again when issue recurs; dealership unable to replicate during service visits.

Coolant flow control valve malfunctions, causing engine overheating and forced shutdown. Vehicle enters limp mode and cannot exceed 5–7 mph. Confirmed by dealer computer diagnostics. Parts on national back order with no ETA, leaving owners stranded.

When: Various timeframes; April 2025 noted in one case; affects vehicles in use

Symptoms owners cite: Check engine light illuminates; Engine overheating warning; Vehicle limited to 5–7 mph maximum speed; Vehicle dies if driven faster; Coolant flow control valve diagnosed by computer test

Codes mentioned: Coolant flow control valve malfunction (confirmed via dealer computer diagnostic)

Repairs/costs cited: Parts on national back order with no ETA. Dealers unable to provide timeline for repair. One owner stranded on vacation for weeks; had to rent car to reach home. Another reset at dealership in one state, failed again 200+ miles away.

Recalls/TSBs owners mention: Dealers acknowledge part is on national back order. No expedited timeline offered. GMC not providing support or rental assistance in cases reviewed.

Lifters on one or both cylinder banks fail, producing knocking or ticking noises. Typically an early sign of impending catastrophic engine failure. Despite lifter replacement, knocking continues, and engine replacement is ultimately required.

When: At 20k–24k miles; soon after purchase or within months

Symptoms owners cite: Knocking or ticking noises from engine; Persistent even after first lifter replacement; No warning light indication initially; Could have resulted in engine seizure if driven far

Repairs/costs cited: Dealer replaces driver-side lifters first; knocking persists. Full engine replacement ordered. Parts on back order; owner waited 15 days in shop, then 30 additional days for engine arrival. Dealer mentioned without confirming.

Recalls/TSBs owners mention: GMC dealer diagnoses and schedules engine replacement; owner denied vehicle replacement or refund. No clear timeline provided; communication from dealership poor.

Oil cap found loose after recall service, allowing oil to leak or escape. One case involves burned transmission fluid odor entering cabin, with oil stains found on ground. Dealer replaced valve body and transmission components before discovering loose cap as the actual cause.

When: Post-recall service; discovered at 8.5k miles in one case

Symptoms owners cite: Burned transmission fluid or engine oil smell in cabin; Oil stains on ground beneath vehicle; Oil cap loose or missing

Repairs/costs cited: Dealer replaces valve body, torque converter, valve body again, checks fluid levels, and replaces transmission filter before discovering loose oil cap. Vehicle remains unrepaired at dealership.

Recalls/TSBs owners mention: Recall 25V-274 directs replacement of oil filler cap with new specification-labeled cap. Loose or defective caps may not be secured properly after dealership service.

Transmission slips in 1st or 2nd gear, causing jerking and abrupt loss of power. Vehicle cannot properly engage gears, resulting in harsh starts and unpredictable acceleration.

When: Various mileages; one case at 97k miles

Symptoms owners cite: Transmission slipping in 1st and 2nd gear; Jerking motion; Vehicle attempts to accelerate but slips; No warning light illuminated in some cases

Repairs/costs cited: Valve body replacement needed but not completed (back order or owner did not pursue).

Recalls/TSBs owners mention: Manufacturer aware; advised owner to file NHTSA complaint.

Metal shavings and internal defects found in engine during replacement or rebuild. Indicates bearing wear, crankshaft, or connecting rod failure. Engine replacement and transmission rebuild required. Represents systemic manufacturing flaw in L87 6.2L V8 engine.

When: At 26k miles in one documented case

Symptoms owners cite: Catastrophic engine failure; Metal shavings in coolant / engine oil; Engine contamination confirmed during teardown

Repairs/costs cited: Full engine replacement and transmission rebuild performed at dealership (Ed Martin GMC, Carmel, IN). New engine running fine but reliability concerns remain due to same defects reported by other owners.

Recalls/TSBs owners mention: Engine replacement and transmission repair covered under warranty. No recall notification or proactive replacement offered; owner discovered defect after failure.

After engine replacement under recall warranty, throttle body stops working. Vehicle is again immobilized and requires dealership repair.

When: Days after engine replacement

Symptoms owners cite: Throttle body stops responding; Vehicle unable to move

Repairs/costs cited: Certified GM dealership replaces throttle body.

Recalls/TSBs owners mention: Dealership repair performed; suggests possible contamination or electrical issue introduced during engine replacement process.

Gear shift control module or TCM fails, causing vehicle to lose transmission control. Check engine light and powertrain warning lights illuminate. Multiple electrical issues occur in same vehicle (failed control module, shortened wire harness, fuel control module).

When: At 21k miles (gear shift control module failure); multiple occurrences in single vehicle across 35k miles

Symptoms owners cite: Check engine light and powertrain warning light illuminate; Vehicle sputtering and erratic shifting; Vehicle enters limp mode; Service Engine Soon message displayed; Electrical faults preventing transmission operation

Codes mentioned: P0700 (Engine Control Module / Transmission fault), Unknown part code requiring cleaning installation

Repairs/costs cited: Gear shift control module replaced at second dealership (original could not source part). TCM update and unknown transmission cleaning part installation attempted at first dealership but not completed. Multiple electrical repairs needed: fuel control module, DEF fluid tank, shortened wire harness.

Recalls/TSBs owners mention: Manufacturer made aware and referred owner to dealer. Parts back order, national supply issues, and extended repair timelines (6–12 weeks minimum, potentially 10–12 weeks) reported.

OnStar system and wireless connectivity fail during or after engine failure event. Control module failure occurs. Requires dealership service and account reconfiguration.

When: Post-engine failure and during engine replacement

Symptoms owners cite: OnStar system non-functional; Wireless connectivity loss; Control module failure

Repairs/costs cited: Bad control module identified and replaced. Owner required additional time post-repair to restore OnStar account to working order.

Recalls/TSBs owners mention: Dealership sourced and installed replacement control module.

After recall remedy (0W-40 oil change), owner reports persistent burning oil smell inside cabin, especially during highway driving. Fumes intensify, forcing owner to drive with windows down.

When: Six months post-recall remedy

Symptoms owners cite: Burning oil smell inside truck cabin; Fumes intensify during highway driving; Smell enters through ventilation

Repairs/costs cited: Owner plans inspection at next oil change; no repair yet completed.

Recalls/TSBs owners mention: Recall remedy specified 0W-40 oil; complaint suggests high-viscosity oil causing excessive heat/fume production or combustion issues.

Tailgate opens unintentionally from storage console switch, which can be easily bumped. No warning light or message alerts driver. Cargo could fall out and strike following vehicles.

When: Occurred at least once in one vehicle

Symptoms owners cite: Tailgate opens without driver input; No warning light or dashboard message; Switch located in easy-to-bump location

Repairs/costs cited: None cited; mentioned as a known concern for the vehicle.

Recalls/TSBs owners mention: No recall issued for this defect as of complaint date. Owner notes combined risk with transmission failure (rear wheel lock-up).

Heater core coolant hose routed by manufacturer so that it rubs on frame. Causes hose wear, coolant leak, and engine overheating. Dealer indicates problem persists on all vehicles. Replacement hose will contact frame again, causing inevitable future wear and breakage. No permanent solution offered.

When: Occurrence date not specified

Symptoms owners cite: Large coolant leak from right side of engine compartment; Temperature warning on dash; Hose wear from rubbing on frame

Repairs/costs cited: Dealership indicates only replacement hose available; no routing fix or protective sleeve offered. Hose replacement not covered under warranty per owner.

Recalls/TSBs owners mention: Dealership acknowledges problem affects all vehicles; offers hose replacement only. No warranty coverage or long-term fix provided.