GMC Sierra 1500 T1XX

3.0L inline-six diesel with aluminum block and single VGT turbo — the only I6 diesel in a US half-ton. Quiet, torque-rich and economical: 22-26 mpg unloaded on the highway. The early run (2020-2022) had several unusual design flaws: a factory-bent camshaft reluctor wheel caused crank-no-start (DTC P0341), and the first-generation timing chain stretched from poor lubrication at the rear of the block. The oil pump is driven by a wet belt running in oil that comes due at 95,000-150,000 miles — and the transmission has to come out to replace it. For 2022 GM revised the chain and reluctor, and for 2023 the LZ0 with steel pistons and a stronger turbo resolved most issues. Solid once the early-build gremlins are sorted — documented service history and a confirmed reluctor/chain status are key when buying.

• !! Crank-no-start: bent reluctor wheel (2020-2022) from 20,000 km

  Factory-bent camshaft reluctor wheel: if the engine stops in exactly the wrong position it cranks without firing (DTC P0341). Replacing the trigger wheel requires cab/transmission removal (40+ hours); a calibration is often tried first.

  Symptoms: Engine cranks 10-20 seconds or won't start at all, usually intermittent; check-engine light with DTC P0341. Often appears soon after purchase.
  0–6,000 $
  Ad camshaft reluctor wheel LM2 3.0 Duramaxcamshaft trigger wheel 3.0 Duramaxcalibration PIP5823B no start
• !! Timing chain stretch, early build (2020-2021) from 100,000 km

  The first-gen chain stretches from poor lubrication at the rear of the block — a camshaft cover let oil bypass the PCV system. Measured at 5.8 mm of slack across 52 links. Throws off valve timing, in extreme cases engine failure (~$10,000). GM revised it for 2021/2022.

  Symptoms: Rattle at the rear of the engine, power loss, timing-correlation fault codes; metal debris in the oil in advanced stages.
  3,000–9,000 $
  Ad timing chain 3.0 Duramax LM2revised timing chain kit 3.0 Duramaxcamshaft cover 3.0 Duramax PCV
• !! Rear Main Seal Leak from 50,000 km

  Seal leaks on early LM2 (2020-2022). Oil spots under the vehicle.

  Symptoms: Oil spots under vehicle, dropping oil level
  800–2,500 $
  Ad 40009072 GM rear main seal 3.0 Duramax LM255506777 GM rear main seal LM2

+ 4 more engine weaknesses + vehicle weaknesses

5.3L V8 EcoTec3, cast-iron block, the highest-volume truck V8 in North America. DFM can shut down up to 14 of 16 firing events — and those constantly cycling lifters are the weak point. While deactivated the needle bearings starve, chatter across the cams and send metal debris through the oil system all the way to a grenaded engine. A nationwide class action is ongoing, with failures spanning from four-digit mileage to 150,000 km. On top of that comes elevated oil consumption via the piston rings and direct-injection carbon buildup. A $200 disabler buys time, a mechanical AFM/DFM delete is the permanent fix. 0W-20 dexos, 8,000 km intervals max — and check the oil level often.

• !! AFM/DFM lifter failure — class action from 100,000 km

  THE GM truck problem: while deactivated, the cylinder-deactivation lifters wear out from oil starvation. The needle bearing scores the camshaft, metal debris enters the oil, a pushrod bends. Nationwide class action; failures from four-digit mileage up to 150,000 km.

  Symptoms: Ticking/knocking from the valvetrain, misfires, shuddering, power loss, check-engine light, in extreme cases total engine failure.
  1,200–8,500 $
  Ad AFM DFM lifter set 5.3 V8 L84cylinder deactivation lifter 5.3DFM delete kit L84camshaft 5.3 EcoTec3pushrod 5.3 V8
• !! Elevated oil consumption from 120,000 km

  Like the earlier V8s, the EcoTec3 5.3 tends toward elevated oil consumption: AFM oil spray nozzles and piston rings let oil into the combustion chamber, roughly 1 litre per 3,000 km in bad cases. The big GM oil-consumption settlements covered the older Gen IV 5.3, not this engine directly — but the EcoTec3 shows the same behaviour.

  Symptoms: Falling oil level between changes, blue smoke on load changes, oil-fouled plugs, oil-pressure light, power loss.
  2,000–6,000 $
  Ad 12698946 AFM lifter L84 5.3LHastings 2M5380 piston ring set Gen V 5.3L
• !! Timing Chain Wear from 160,000 km

  Timing chain and guides wear at high mileage from ~160,000 km — accelerated by long oil intervals. A rattle on cold start is the first warning sign.

  Symptoms: Rattle/chain rattle on cold start, check-engine light (cam/crank correlation P0008/P0016), rough running.
  1,000–2,500 $
  Ad 12630107 timing chain tensioner Gen V LT12680750 timing chain kit 5.3L EcoTec312713934 crankshaft sprocket gear Gen V

+ 1 more engine weaknesses + vehicle weaknesses

6.2L V8 EcoTec3, 420 hp, same Gen V architecture as the 5.3 but with a deeper exhaust note and noticeably more shove. On the 2021–2024 build years the manufacturing process left metal debris and out-of-spec connecting-rod/crankshaft parts in roughly 600,000 engines — bearing failure without warning, in the worst case loss of propulsion while driving. GM's recall fix was a switch to 0W-40 oil, which doesn't address the root cause; NHTSA is investigating continued failures, including the excluded 2019–2020 trucks. Add the same DFM lifter risk as the 5.3 plus oil consumption. Pre-2021 examples or confirmed post-recall engines with a complete oil-change history are the ones to buy.

• !! Recall: rod-bearing / crankshaft defect — approx. 600,000 vehicles

  Manufacturing faults in the connecting rods and crankshaft (out of spec, machining debris in the oil galleries) destroy the bearings — engine failure without warning, in extreme cases loss of propulsion while driving. Affects 2021–2024 L87. GM fix: free inspection, engine replacement if needed, otherwise a switch to 0W-40 oil. NHTSA is investigating continued failures.

  Symptoms: Knocking/tapping, sudden loss of power or propulsion, oil-pressure warning, metal particles in the oil, in extreme cases a stall while driving.
  0–0 $
  Ad L87 rod bearing set 6.2crankshaft 6.2 V8 L87replacement engine 6.2 L87Mobil 1 FS 0W-40
• !! AFM/DFM lifter failure from 100,000 km

  Same lifter issue as the 5.3L: the cylinder-deactivation lifters collapse or stick, a pushrod bends, metal debris enters the oil. Also affects the 2019–2020 trucks excluded from the rod-bearing recall — cam/lifter damage there as early as 55,000 km, clustering around 145,000 km.

  Symptoms: Ticking/knocking from the valvetrain, misfires, power loss, check-engine light, rough running, in extreme cases engine failure.
  2,500–8,500 $
  Ad AFM DFM lifter set 6.2 V8 L87cylinder deactivation lifter 6.2DFM delete kit L87camshaft 6.2 EcoTec3
• !! Oil Consumption — Piston Rings (2019-2020 and older L87) from 120,000 km

  Piston rings and AFM oil nozzles pass oil — 0.5–1 litre per 3,000 km in bad cases. Especially affects the 2019–2020 L87 not covered by the rod-bearing recall. NHTSA is investigating these earlier years in a separate probe.

  Symptoms: Falling oil level between changes, blue smoke, oil-fouled plugs, oil-pressure light, in extreme cases knocking from oil starvation.
  2,500–7,000 $
  Ad piston rings GM 5.3 L84oil consumption fix Silverado

+ 1 more engine weaknesses + vehicle weaknesses

2.7-liter turbo four-cylinder, aluminum block, direct injection only — GM's answer to Ford's EcoBoost. 310 hp and 400 lb-ft from just 1,500 rpm, feels like a small V8 down low until revs climb and the four-cylinder character shows through. Runs AFM cylinder deactivation (cylinders 2 and 3 shut off under light load), which acts up far less than on the V8s but can stick lifters if oil changes are neglected. Head gasket failures on the 2019-2022 early run under 25,000 miles, mostly warranty-covered. Direct injection demands walnut blasting of the intake valves, with the high-pressure pump and injectors being the usual turbo-DI wear items. Short oil-change intervals with Dexos oil are mandatory here; well-kept 2022+ examples run trouble-free.

• !! Head Gasket on Early Models (2019-2022) from 40,000 km

  Early L3B engines (2019-2022) can lose the head gasket as soon as 20,000-40,000 miles. Coolant intrudes into the cylinders, in the worst case pitting the cylinder walls and requiring an engine swap. Usually covered under the powertrain warranty.

  Symptoms: White smoke, overheating, milky oil
  1,500–4,500 $
  Ad head gasket L3B 2.7 turbo Silveradooil cooler block gasket L3B 2.7
• !! AFM lifter / cylinder deactivation from 100,000 km

  The AFM cylinder deactivation shuts off cylinders 2 and 3 under light load. In the deactivated state the lifters can stick or wear with thin or cold oil — far rarer than on the V8s, but documented and part of a class action. GM covers repairs through extended warranties.

  Symptoms: Hard misfires especially at idle or when cylinders re-engage, power loss, stumbling, increased oil consumption.
  1,500–4,000 $
  Ad AFM lifter set 2.7 L3Bhydraulic lifter L3B TurboMaxAFM lifter kit L3B 2.7
• !! Recall: cracked block (oil gallery) N232415060

  A casting flaw can crack the engine block's main oil gallery. Result: loss of oil pressure and catastrophic engine failure. Customer Satisfaction Program N232415060 for the 2023 run, only a few VINs confirmed, free engine replacement.

  Symptoms: Sudden oil loss, oil-pressure warning, oil traces at the block; for many affected vehicles not noticeable beforehand.
  Ad Customer Satisfaction Program N232415060engine block 2.7 L3B cracked oil galleryN232415060 engine replacement

+ 5 more engine weaknesses + vehicle weaknesses