P0135 on the All-New 2024 Toyota 4Runner
The 2024 Toyota 4Runner is a complete redesign, replacing the long-running fifth generation with the TNGA-F platform. The new 4Runner is powered by the T24A-FTS 2.4-liter turbocharged four-cylinder engine producing 278 horsepower and 317 lb-ft of torque, with an optional i-FORCE MAX hybrid making 326 horsepower. A P0135 code on this new powertrain means the upstream O2 sensor heater circuit has malfunctioned.
New Platform, New Exhaust Layout
The turbocharged inline-four represents a significant departure from the previous 4.0L V6. Since it is a single-bank engine, Bank 1 Sensor 1 is the only upstream O2 sensor. It sits between the exhaust manifold and the turbocharger, in one of the hottest zones of the exhaust system. The turbo generates extreme exhaust gas temperatures that place high thermal demands on the sensor and its heater element.
What Triggers P0135 on the 2024 4Runner
- Manufacturing defect in the O2 sensor (High Likelihood): On a brand-new vehicle, a premature heater failure almost certainly indicates a manufacturing defect. The Denso OEM sensor may have had an internal flaw in the heater coil that caused early failure.
- Thermal stress from turbo proximity (Medium Likelihood): The turbocharger creates extreme heat near the upstream O2 sensor. Aggressive off-road driving with high RPMs or towing can push exhaust temperatures to their limits, stressing the heater element beyond its design margins.
- Wiring or connector issue (Medium Likelihood): The new engine bay has complex routing for wiring harnesses around the turbocharger, intercooler piping, and associated components. A pinched wire or loose connector from factory assembly is possible.
- Off-road water exposure (Low-Medium Likelihood): The 4Runner is designed for off-road use, and water fording on a new vehicle can push water into connector areas. The new platform should have improved sealing, but aggressive water crossings can still cause issues.
Dealer Warranty Repair
Your 2024 4Runner is under full warranty, including the 8-year/80,000-mile federal emissions warranty. This is unquestionably a dealer repair. The new turbo engine's complexity, combined with warranty coverage, makes DIY unnecessary and potentially counterproductive. The dealer will diagnose the heater circuit, check for TSBs on the new platform, and replace the sensor at no cost.
What to Tell the Dealer
Describe when the check engine light appeared, your driving conditions (especially any off-road use, water crossings, or towing), and whether the light is steady or flashing. This information helps the technician narrow the diagnosis efficiently.
Cost Reference
Under warranty: free. Future reference: OEM Denso sensor for the 2.4L turbo costs $100 to $180. Shop labor on the turbo engine is $120 to $200 due to access complexity. Total out-of-pocket after warranty: $220 to $380. The turbo-area sensor location is not suitable for DIY replacement without proper tools and experience.
Off-Road Considerations for the New 4Runner
The 2024 4Runner retains its off-road mission with standard four-wheel drive, locking rear differential on TRD models, and improved approach and departure angles. However, the turbocharged engine introduces new considerations for off-road electrical components. After water fording or deep mud, inspect the sensor area for debris and moisture. The new platform should have better sealing than the previous generation, but no vehicle is completely waterproof.
Do Not Delay
The 2.4L turbo engine relies on precise fuel management for both performance and turbocharger longevity. Running rich during cold starts can contribute to carbon buildup on intake valves and turbo inlet. Since the repair is free under warranty, schedule your dealer visit promptly to maintain optimal engine health.