The 2007 H2 with the 6.0L Vortec (LQ4/LQ9) is a tough truck sharing GMT900 bones with Silverado/Tahoe, but it suffers from active fuel management (AFM) lifter collapse, transmission cooler line corrosion, and occasional catastrophic piston/ring failures tied to oil starvation and detonation.
AFM Lifter Collapse & Cam Lobe Wear
Common · high severityTypical onset: 80,000-150,000 mi
Symptoms: Check engine light with P0300-P0308 misfire codes, Ticking, tapping, or lifter clatter on cold start that may persist, Loss of power, rough idle, Metal shavings in oil, indicating cam damage
Fix: Requires AFM lifter replacement, often with camshaft if lobes are wiped. Many shops disable AFM with tuner to prevent recurrence. 12-18 hours labor for lifters/cam plus tune.
Estimated cost: $2,500-5,000
Transmission Oil Cooler Line Corrosion & Leaks
Common · medium severityTypical onset: 70,000-120,000 mi
Symptoms: Transmission fluid pooling under vehicle, often near radiator, Low trans fluid warning or erratic shifting, Pink or red fluid mixing with coolant (if internal cooler fails)
Fix: Steel lines rust through where they run along frame rails. Replace both lines, not just the leaker. 2-4 hours labor depending on rust severity.
Estimated cost: $400-800
Piston Ring Collapse & Cylinder Scoring
Occasional · high severityTypical onset: 100,000-180,000 mi
Symptoms: Excessive oil consumption (quart every 500-1,000 mi), Blue smoke on acceleration or deceleration, Loss of compression, misfires, Severe cases: knocking, metal in oil, complete failure
Fix: Pistons collapse due to heat, detonation, or oiling issues. Requires full rebuild or short block replacement. 25-35 hours labor, often includes head gasket work.
Estimated cost: $5,000-9,000
Fuel Pump & Filter Failure
Occasional · medium severityTypical onset: 90,000-140,000 mi
Symptoms: Hard starting, especially after sitting, Stalling at idle or under load, Loss of power, surging, Fuel pressure drops below 55 psi
Fix: In-tank pump wears out; filter clogs from rust in steel tank. Drop tank, replace pump module and filter. 3-5 hours labor.
Estimated cost: $600-1,200
Transfer Case Encoder Motor & 4WD Engagement Issues
Common · medium severityTypical onset: 60,000-110,000 mi
Symptoms: Service 4WD message on dash, Unable to engage or disengage 4WD modes, Grinding or clunking from transfer case, 4WD indicator lights flashing
Fix: Encoder motor (shift motor) fails or position sensor drifts. Replace motor and recalibrate. 1.5-2.5 hours labor.
Estimated cost: $400-700
EVAP Vent Valve & Purge Solenoid Codes
Occasional · low severityTypical onset: 80,000-130,000 mi
Symptoms: Check engine light with P0449, P0455, P0496, Fuel smell near tank after fill-up, Rough idle after refueling, Failed emissions test
Fix: Vent valve on top of tank or purge solenoid at engine corrodes. Replace valve/solenoid and check hoses. 1-2 hours labor.
Estimated cost: $250-500
Electrical System: Alternator & Battery Cable Corrosion
Occasional · medium severitySymptoms: Battery drain, no-start conditions, Flickering dash lights, voltage fluctuations, Alternator overcharging (>15V) or undercharging (<13V), Corroded terminals at battery or starter
Fix: High current demand on 6.0L stresses alternator; battery cables corrode at crimps. Replace alternator (2 hours) and inspect/replace positive cable from battery to underhood fuse block.
Estimated cost: $500-900
Buy only if under 80,000 miles with documented AFM lifter replacement or delete, and budget $3,000-5,000 for deferred engine/trans issues.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.