P0175 on the Redesigned 2024 Toyota 4Runner
The 2024 Toyota 4Runner received a complete redesign, moving to the TNGA-F platform with a new 2.4L turbocharged four-cylinder engine (T24A-FTS) producing 278 horsepower and 317 lb-ft of torque. If your new 4Runner is showing a P0175 code, the ECM has determined that Bank 2 is running too rich. While this is technically a four-cylinder engine, the term Bank 2 still applies to the secondary O2 sensor monitoring point in the exhaust system.
Understanding Bank 2 on a Four-Cylinder
On inline four-cylinder engines like the T24A-FTS, the concept of Bank 1 and Bank 2 is different from a V-configuration engine. Some manufacturers use Bank 2 to refer to the downstream (post-catalytic converter) monitoring circuit. If your 2024 4Runner is showing P0175, check whether your scan tool is reporting it as a pre-cat or post-cat issue. On turbocharged engines, the turbocharger sits between the engine and the catalytic converter, adding another variable to exhaust gas analysis.
Symptoms to Watch For
- Check engine light active
- Reduced fuel economy from the expected 21 city / 26 highway MPG ratings
- Black smoke or soot from the exhaust under boost
- Turbo lag or reduced boost response
- Rough idle or occasional misfire sensation
- Exhaust has a strong gasoline odor
Causes Specific to the 2024 4Runner's Turbo Engine
1. MAF Sensor Contamination
The 2024 4Runner's turbocharged engine draws air through the MAF sensor, then through the compressor side of the turbo. Any oil mist from the turbo's bearing seals or from the PCV system can coat the MAF sensor element. Additionally, off-road dust that bypasses the filter element can contaminate the sensor. A dirty MAF under-reports airflow, causing the ECM to calculate a richer mixture than intended.
2. Upstream O2 or Air-Fuel Ratio Sensor
The T24A-FTS uses a wideband air-fuel ratio sensor upstream of the turbocharger. This sensor provides precise readings across a broad range of mixtures. When it degrades, the ECM loses its primary feedback for fuel correction. On a new vehicle, premature failure can be caused by manufacturing defects, coolant contamination, or exposure to silicone-based sealants or certain fuel additives.
3. Boost Pressure Irregularities
The turbocharger on the 2024 4Runner uses an electronic wastegate. If the wastegate actuator sticks or the boost pressure sensor provides incorrect readings, the ECM may over-fuel to match what it believes is a higher airflow than actually exists. This is unique to turbocharged applications and can cause Bank 2 rich codes when the exhaust-side sensor sees unburned fuel.
4. Leaking Direct Fuel Injector
The T24A-FTS uses both direct and port injection. A direct injector that fails to close completely between injection events allows fuel to dribble into the combustion chamber continuously. At idle, this extra fuel is significant enough to skew O2 sensor readings and trigger P0175. Direct injector leaks can also cause oil dilution as fuel washes past the piston rings.
Diagnostic Procedure
- Connect a scan tool and read all stored codes; check for related boost or turbo codes
- Review freeze frame data for engine load, boost pressure, and RPM at the time of the code
- Monitor fuel trim values; on this four-cylinder, compare pre-turbo and post-cat sensor readings
- Inspect and clean the MAF sensor
- Check turbo intercooler piping and charge pipes for leaks or loose connections
- Evaluate the wastegate actuator operation with a bidirectional scan tool
- Test fuel pressure at the direct injection rail
Estimated Repair Costs
MAF cleaning is a free DIY task with a $10 can of cleaner. O2 or air-fuel ratio sensor replacement on the 2024 4Runner costs $200-$400 with parts and labor. Wastegate actuator repair ranges from $300-$700. Direct injector replacement runs $400-$900 per injector due to the high-pressure system and labor involved in accessing them.
Warranty Considerations
As a 2024 model, your 4Runner is under Toyota's 3-year/36,000-mile basic warranty and 5-year/60,000-mile powertrain warranty. A P0175 code on a new vehicle should absolutely be taken to the dealer first. The fuel system and emissions-related components are covered, and Toyota will diagnose and repair at no cost if it is a manufacturing defect or premature component failure.