P0175 on the 2023 Toyota Highlander
A P0175 code on your 2023 Toyota Highlander indicates bank 2 is running rich — excess fuel in the combustion mixture. The 2023 Highlander received a significant update, replacing the 3.5L V6 with a new 2.4L turbocharged four-cylinder engine (265 hp, 310 lb-ft) paired with an 8-speed automatic. The hybrid continues with the 2.5L Atkinson-cycle engine. P0175 applies primarily to the 2.4T. On a nearly new vehicle, this is almost certainly a warranty-covered issue.
Symptoms
- Check engine light illuminated
- Fuel smell from the exhaust
- Rough or unsteady idle
- Black soot at the tailpipe
- Fuel economy below the rated 22–26 mpg
- Turbo may feel sluggish
Causes on the 2023 Highlander
1. Defective O2/Air-Fuel Ratio Sensor (High Likelihood)
A factory-defective sensor on the 2.4T engine that reads falsely lean causes the ECM to add excess fuel. The 2.4L turbo uses wideband sensors for precise monitoring under varying boost conditions. As a first-year turbo application in the Highlander, early sensor issues are possible. The dealer can verify sensor output against Toyota's specifications.
2. Fuel Injector Issue (Medium Likelihood)
The 2.4T uses direct fuel injection operating at very high pressures. A manufacturing defect in an injector seal or needle valve can allow fuel to drip between injection events. The turbocharged engine's higher combustion pressures put more stress on injector sealing. An injector leak-down test identifies the faulty unit.
3. Fuel Pressure or Boost-Related Calibration (Medium Likelihood)
The 2.4T's fuel pressure management is more complex than the previous V6's due to turbocharger boost. A faulty fuel pressure sensor, boost-dependent fueling calibration error, or HPFP issue can cause excess fuel delivery. Toyota may have released a software update for the first-year 2.4T application.
4. EVAP Purge Valve Defect (Low Likelihood)
A purge valve stuck open feeds fuel vapor into the intake. Straightforward warranty repair on a new vehicle.
Diagnostic Steps
- Check for TSBs — Critical for the first-year 2.4T in the Highlander.
- Monitor fuel trims — Negative LTFT below -8% confirms rich condition.
- Test sensors — Verify output against specifications under various boost conditions.
- Check fuel pressure — Monitor across idle, partial throttle, and full boost.
- Test EVAP system — Verify purge valve operation.
Cost Estimates (Reference)
- O2/A-F sensor: $120–$300
- Fuel injector: $160–$420
- Fuel pressure sensor/HPFP: $150–$400
- EVAP purge valve: $80–$190
Full Warranty Coverage
The 2023 Highlander is covered by Toyota's 3-year/36,000-mile basic warranty and 5-year/60,000-mile powertrain warranty. The 2.4T engine and all emissions components are fully covered. O2 sensors have 8-year federal emissions coverage. Take it to your Toyota dealer for a free repair.
New Engine, No Worries
The 2.4T is Toyota's new generation of turbo engines, replacing the larger V6. While any new engine design can have early-production component issues, Toyota's engineering quality means P0175 is an individual component problem, not a design deficiency. The dealer will diagnose and repair under warranty, and your Highlander should return to perfect operation.