The 2009 G6 is a competent mid-size sedan undermined by chronic transmission failures (especially 6T70/6T75 six-speeds) and catastrophic 3.5L/3.9L V6 engine failures due to intake manifold gasket defects allowing coolant into cylinders. The 2.4L four-cylinder is notably more reliable.
6-Speed Automatic Transmission Failure (6T70/6T75)
Common · high severityTypical onset: 80,000-130,000 mi
Symptoms: Hard or delayed 2-3 upshifts, flaring between gears, Shuddering during light acceleration or torque converter lockup, Transmission slipping, especially when warm, Check engine light with P0776 (pressure control solenoid), P0735 (gear ratio incorrect), Metal debris in pan during fluid changes
Fix: Transmission rebuild or replacement required; internal clutch pack failure and valve body issues are root causes. Remanufactured unit swap is 6-8 hours labor, rebuild is 12-16 hours. Used transmissions are a gamble—often fail within 20k miles.
Estimated cost: $2,800-4,500
Intake Manifold Gasket Failure Leading to Engine Destruction (3.5L/3.9L V6)
Common · high severityTypical onset: 60,000-110,000 mi
Symptoms: White smoke from exhaust, especially on cold starts, Overheating with no external coolant leaks, Rapid coolant loss into crankcase—milky oil on dipstick, Misfire codes and rough idle, Catastrophic hydrolock if coolant floods cylinders overnight
Fix: Lower intake manifold gasket replacement is 6-8 hours labor if caught early ($800-1,200). If coolant ingestion damages bearings or cylinders, you're looking at short block replacement (18-24 hours) or complete engine swap (14-18 hours). Many engines are junked at this point—repair exceeds vehicle value.
Estimated cost: $800-6,500
Power Steering Electric Assist Failure
Occasional · high severityTypical onset: 70,000-120,000 mi
Symptoms: Complete loss of power steering assist—extremely heavy steering, Power steering warning light illuminated, No warning before failure in many cases, Diagnostic codes C0545, C0899 stored
Fix: Electric power steering motor/ECU assembly replacement is the fix; no rebuild option available. Part is 2.5-3.5 hours labor. GM issued recalls on some VINs but not comprehensive coverage. Aftermarket units are hit-or-miss on longevity.
Estimated cost: $800-1,400
Transmission Shift Cable and PRNDL Indicator Issues
Common · medium severityTypical onset: 50,000-90,000 mi
Symptoms: Gear indicator showing wrong gear (Park when in Drive, etc.), Key stuck in ignition—won't recognize Park position, Shifter feels loose or disconnected, Vehicle rolls when placed in Park
Fix: Shift cable bushing at transmission end wears out; GM recall 14311 addressed some units but not all. Cable replacement is 1.5-2 hours labor. Also check ignition lock cylinder interlock—separate failure point. Safety issue if vehicle isn't truly in Park.
Estimated cost: $250-450
Timing Chain Stretch and Tensioner Failure (2.4L I4 Ecotec)
Occasional · high severityTypical onset: 100,000-150,000 mi
Symptoms: Rattling noise from engine on cold start, lasting 5-15 seconds, Check engine light with P0008, P0009 (cam/crank correlation), Rough idle and loss of power, Engine stalling or failing to start if chain skips teeth
Fix: Timing chain, guides, tensioner, and VVT actuators replacement required. 8-10 hours labor—front-wheel-drive configuration makes access difficult. If chain jumps time, valve-to-piston contact causes internal damage requiring head work or engine replacement.
Estimated cost: $1,200-2,200
Water Pump Failure (All Engines)
Occasional · medium severityTypical onset: 70,000-100,000 mi
Symptoms: Coolant leak from weep hole at front of engine, Squealing or grinding noise from serpentine belt area, Overheating under load or in traffic, Low coolant warning light
Fix: Water pump replacement is 3-4 hours on V6 engines, 2.5-3 hours on 2.4L. Replace thermostat and flush system at same time. On 3.5L/3.9L, inspect intake gaskets closely—coolant leaks often mask gasket failure.
Estimated cost: $450-750
Ignition Lock Cylinder and Key Sensor Failures
Occasional · medium severityTypical onset: Any mileage
Symptoms: Key won't turn or gets stuck in ignition, Security light flashing—engine cranks but won't start, Intermittent no-start requiring 10-minute wait, Steering wheel lock engaging at random
Fix: Passlock system failure common across GM platforms. Ignition lock cylinder replacement is 1-1.5 hours but requires reprogramming. Some techs do resistor bypass (not recommended for security). GM TSB addresses relearn procedure but doesn't fix worn tumblers.
Estimated cost: $300-600
Hard pass unless it's a 2.4L four-cylinder with documented transmission service under 60k miles and priced under $4,000—even then, keep a repair fund ready.
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.