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2012 TOYOTA 4RUNNER

4.0L V6•4WD•AUTOMATIC•gas
5-Year Cost of Ownership
$12,403 maintenance + known platform issues
~$2,481/yr · 210¢/mile equivalent · $5,470 maintenance + $6,233 expected platform issues
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4.7L V8
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Common Problems & Known Issues

The 2012 4Runner with the 4.0L V6 is generally reliable but suffers from a catastrophic secondary air injection system failure that can grenade the engine, plus typical 4WD and exhaust manifold issues common to this generation.

Secondary Air Injection Pump Failure Leading to Complete Engine Destruction

Occasional · high severity
Typical onset: 80,000-150,000 mi
Symptoms: Check engine light with P0418/P0419 secondary air codes, Sudden catastrophic knocking and loss of power after air pump disintegrates, Metal shavings throughout intake manifold and cylinders, Complete engine seizure in worst cases
Fix: When the secondary air pump impeller disintegrates, metal debris enters intake runners and destroys pistons, rings, and cylinder walls. Many shops see complete engine rebuilds or replacements. Short block or long block replacement requires 18-25 hours labor depending on access and damage extent. Preventive replacement of air pump assembly at first sign of noise runs 3-4 hours.
Estimated cost: $6,500-12,000

Exhaust Manifold Cracking and Stud Failure

Common · medium severity
Typical onset: 60,000-120,000 mi
Symptoms: Ticking noise from engine bay on cold starts that may diminish when warm, Exhaust smell in cabin, Check engine light with lean codes if leak is severe, Visible cracks or broken studs on manifold inspection
Fix: The factory exhaust manifolds crack at the collector or studs snap off in the head. Requires manifold replacement and often drilling/extracting broken studs. Figure 6-8 hours per side for manifold, gaskets, and stud extraction. Both sides often need addressing eventually.
Estimated cost: $1,200-2,400

Transmission Oil Cooler Line Corrosion and Leaks

Common · medium severity
Typical onset: 90,000-140,000 mi
Symptoms: Transmission fluid dripping from front of vehicle, Low transmission fluid level on dipstick, Burnt transmission smell if fluid level drops significantly, Pink or red fluid pooling under radiator area
Fix: The hard transmission cooler lines corrode where they run along the frame, especially in salt states. Line replacement requires removing skid plates and sometimes exhaust sections for access. 3-4 hours labor plus flushing and refilling the transmission.
Estimated cost: $600-1,200

Front Lower Ball Joint Wear

Common · high severity
Typical onset: 70,000-110,000 mi
Symptoms: Clunking from front suspension over bumps, Loose or wandering steering feel, Excessive play when prying on tire at 6 and 12 o'clock positions, Uneven inner tire wear
Fix: The front lower ball joints wear prematurely, especially with oversized tires or off-road use. Requires pressing out old joints and installing new ones, or replacing entire lower control arm assemblies. 2.5-3.5 hours per side including alignment.
Estimated cost: $800-1,400

Transfer Case Actuator Motor Failure

Occasional · medium severity
Typical onset: 80,000-130,000 mi
Symptoms: Flashing 4WD lights on dash with inability to engage 4WD, Grinding or whirring noise from under vehicle when attempting 4WD engagement, Transfer case stuck in 4WD high or low, Error codes related to transfer case shift actuator
Fix: The electric shift motor on the transfer case fails, leaving you stuck in 2WD or unable to disengage 4WD. Motor replacement requires dropping the front driveshaft and accessing the actuator from underneath. 2-3 hours labor for motor only; more if internal transfer case damage occurred from forcing shifts.
Estimated cost: $500-900

Running Board Motor and Linkage Failure

Occasional · low severity
Typical onset: 60,000-100,000 mi
Symptoms: Power running boards fail to deploy or retract, Grinding or clicking noise from running board motors, Boards stuck in extended or retracted position, One side works while other doesn't
Fix: If equipped with power running boards, the motors and plastic linkages fail from corrosion and repeated cycling. Motor replacement is straightforward at 1.5-2 hours per side, but often both sides need attention within short intervals. Many owners disable them entirely or retrofit fixed boards.
Estimated cost: $600-1,000
Owner tips
  • Replace secondary air injection pump at first sign of noise or bearing roughness—preventive replacement is infinitely cheaper than engine rebuild
  • Inspect exhaust manifolds annually for cracks and address early before studs break off in the head
  • Undercoat or fluid-film the transmission cooler lines in rust-belt states to extend their life
  • Upgrade to aftermarket heavy-duty lower ball joints if you run oversized tires or do serious off-roading
  • Use Toyota ATF-WS only in the transmission—substitute fluids cause premature wear in the valve body
Buy one if you can verify the secondary air pump has been addressed and exhaust manifolds aren't cracked—otherwise budget $8k-10k for potential engine work on top of purchase price.
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.
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