2020 GMC CANYON

Typical onset: 40,000-80,000 mi

Symptoms: Sudden loss of power, loud knocking from crankcase, White or blue smoke from exhaust, oil consumption spikes, Check engine light with low compression codes (P0300-range misfires), Metal shavings in oil, coolant contamination

Fix: GM issued TSB 20-NA-206 acknowledging piston crown failures on 2020 Duramax engines. Pistons crack at the bowl rim, leading to rod bearing damage, crankshaft scoring, and often complete bottom-end destruction. Repair requires full shortblock replacement or engine rebuild with updated pistons—expect 18-24 labor hours for R&R and rebuild. Some dealers doing longblocks under extended goodwill warranty, but out-of-warranty owners face catastrophic bills.

Estimated cost: $8,000-14,000

Typical onset: 50,000-90,000 mi

Symptoms: Transmission fluid pooling under vehicle, usually driver side, Burnt ATF smell, transmission running hotter than normal, Low fluid warning or limp mode if leak progresses, Visible fluid on cooler lines at radiator or along frame rail

Fix: The cooler lines for the 8L45/8L90 transmission develop leaks at crimped fittings or where lines rub frame rails. Often affects both feed and return lines. Replacement involves dropping skid plates, routing new lines—about 3-4 hours labor. Use OEM lines; aftermarket fittings leak quickly. Flush cooler and verify no metal in pan while you're in there.

Estimated cost: $600-1,100

Typical onset: 60,000-100,000 mi

Symptoms: Clunk or thud on hard acceleration or deceleration, Vibration at idle in gear, especially in Reverse, Visible sagging or torn rubber on crossmember mount, Driveline shudder during gear changes

Fix: The rear transmission crossmember mount tears from torque cycling, especially on V6 models with towing. Mount is a large rubber-isolated affair—replacement requires supporting the transmission, dropping the crossmember, swapping the mount. About 2 hours labor. Inspect driveshaft U-joints while you're under there, as the added movement accelerates their wear.

Estimated cost: $350-650

Symptoms: Hard starting, especially in cold weather, Loss of power under load, surging at highway speeds, Water-in-fuel warning light illuminated, Rough idle, white smoke during cold starts

Fix: The 2.8L Duramax uses a canister filter housing that's prone to water accumulation if fuel quality is poor or drain intervals are skipped. Contaminated fuel accelerates injector wear. Replace filter and prime system—about 0.8 hours labor. If injectors are affected, you're looking at $2,500+ for a set of four. Always drain the water separator every oil change on the diesel.

Estimated cost: $150-300

Typical onset: 120,000-180,000 mi

Symptoms: Cold-start rattle from front of engine for 2-3 seconds, Check engine light with cam/crank correlation codes (P0008, P0011), Rough idle, loss of power at higher RPMs, Metal debris in oil if chain has been slapping guides

Fix: The 3.6L LGZ/LCV uses a long-life chain, but neglected oil changes cause premature stretch. Requires timing cover removal, both chains, guides, tensioners, and usually VVT actuators—10-14 hours labor. Not common if oil was changed every 5k, but skipping services accelerates wear. Inspect oil pump drive chain while you're in there.

Estimated cost: $2,200-3,800