The 2009 DB9's naturally-aspirated 6.0L V12 is fundamentally robust, but failures in the transmission cooling system and catastrophic engine damage from dropped valve seats plague these cars. Expect exotic-car maintenance costs and hunt for meticulous service history.
Dropped Valve Seats / Catastrophic Engine Failure
Occasional · high severityTypical onset: 40,000-80,000 mi
Symptoms: Sudden rough idle or misfires on one bank, Metallic rattling from engine bay at startup, Check engine light with multiple cylinder misfire codes, Catastrophic loss of compression leading to complete engine failure
Fix: Valve seats separate from aluminum heads due to inadequate interference fit from factory. Requires full engine-out rebuild with upgraded seat installation, new pistons often needed due to collateral damage. 60-80 labor hours for proper fix.
Estimated cost: $25,000-45,000
Transmission Oil Cooler Failure
Common · high severityTypical onset: 50,000-90,000 mi
Symptoms: Transmission fluid mixing with coolant (strawberry milkshake in expansion tank), Slipping gears or delayed engagement, Overheating transmission temperature warnings, Loss of drive after coolant contamination
Fix: Internal cooler in radiator fails, cross-contaminates fluids. Requires radiator replacement, complete transmission flush and filter service, sometimes full trans rebuild if contamination severe. 8-12 hours labor plus parts.
Estimated cost: $3,500-8,500
Transmission Control Module Failure
Occasional · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Stuck in one gear (usually 2nd or 5th), Harsh shifting or refusal to shift, Transmission warning light illuminated, Limp mode activation with no actual mechanical fault
Fix: TCM located under transmission gets heat-soaked and fails. Replacement requires transmission drop for access. 6-8 hours labor, module must be programmed to VIN.
Estimated cost: $2,200-3,800
Accelerator Pedal Position Sensor Failure
Common · medium severitySymptoms: Intermittent throttle response or dead pedal, Check engine light with throttle position codes, Engine cuts power suddenly while driving, Limp mode with reduced throttle input
Fix: Pedal assembly sensor fails, subject to recall but many units still problematic. Complete pedal assembly replacement required, cannot repair sensor alone. 2-3 hours labor.
Estimated cost: $800-1,400
Transmission Mounts Deterioration
Common · low severityTypical onset: 50,000-90,000 mi
Symptoms: Clunking when shifting from Park to Drive, Excessive driveline vibration at idle in gear, Visible transmission sag or misalignment, Harsh engagement into reverse
Fix: Hydraulic transmission mounts collapse from age and heat. Requires full exhaust removal for access to rear mount. Front mount easier. 4-6 hours for both mounts.
Estimated cost: $1,200-2,200
Fuel Filter Clogging / Fuel Pump Failure
Occasional · medium severityTypical onset: 60,000-120,000 mi
Symptoms: Hesitation or stumble under hard acceleration, Difficulty starting when fuel tank below quarter-full, Loss of power at highway speeds, Fuel pump whine audible from rear of car
Fix: In-tank fuel filter not routinely serviced leads to pump starvation. Requires rear subframe drop and tank removal for proper access. 8-10 hours labor, replace pump and filter together.
Estimated cost: $2,000-3,500
Battery Cable Corrosion / Electrical Gremlins
Common · low severitySymptoms: Intermittent no-start conditions, Random warning lights on dash, Modules failing to communicate (especially seat heaters), Parasitic battery drain
Fix: Battery cables and grounds corrode at junction box in footwell. Clean all connections, apply dielectric grease, sometimes requires cable replacement. Subject to recall but ongoing issue. 2-4 hours diagnosis and repair.
Estimated cost: $400-900
Buy only with comprehensive service records and a valve-seat inspection; the trans cooler will fail, but the engine grenading is the real financial nuclear bomb.
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.