What P0175 Means on the 2021 Toyota Highlander
The P0175 code on your 2021 Toyota Highlander indicates bank 2 is running rich — too much fuel relative to air. The 2021 Highlander (4th generation) is available with the 2.5L Dynamic Force four-cylinder hybrid (243 hp combined) or the 3.5L 2GR-FKS V6 (295 hp) with D-4S dual injection. The P0175 code is most relevant to the V6, which has a distinct bank 2 cylinder group. On the 2.5L hybrid, fuel system codes may present differently.
Symptoms
- Check engine light on
- Fuel smell from the exhaust
- Rough idle noticeable in the quiet cabin
- Black soot at the dual exhaust tips
- Fuel economy below the rated 20–29 mpg
- Possible misfires or stumble
Common Causes on the 2021 Highlander
1. O2 Sensor Issue on Bank 2 (High Likelihood)
The 3.5L V6 has dedicated O2 sensors for each bank. The bank 2 upstream air-fuel ratio sensor controls fuel delivery for the rear cylinder bank. At 3-5 years old, premature sensor failure can occur. A sensor reading falsely lean causes the ECM to add excess fuel. Compare bank 1 and bank 2 sensor performance with a scan tool to identify discrepancies.
2. Leaking Bank 2 Fuel Injector (Medium Likelihood)
The 3.5L D-4S V6 uses both port and direct injectors per cylinder. A leaking injector on bank 2 (rear) delivers excess fuel to that bank specifically. Direct injectors are more susceptible to carbon buildup and seal issues. Check bank 2 spark plugs for fuel fouling to identify the affected cylinder.
3. Fuel Pressure Control Fault (Medium Likelihood)
The D-4S dual fuel system on the 3.5L V6 manages both low-pressure port injection and high-pressure direct injection. A faulty pressure sensor or control valve can cause elevated pressure on bank 2's fuel supply. Monitor fuel rail pressure with the dealer's scan tool.
4. MAF Sensor Overreading (Low Likelihood)
An overreading MAF sensor causes the ECM to inject too much fuel across both banks. If only P0175 is present (without P0172), focus on bank 2-specific causes first. Clean the MAF as a low-cost diagnostic step.
Diagnostic Steps
- Identify your engine — V6 or hybrid 2.5L, as diagnostics differ significantly.
- Check for companion codes — P0172 alongside P0175 means both banks rich (systemic issue).
- Compare bank fuel trims — A significant LTFT split between banks indicates a bank-specific problem.
- Test O2 sensors — Compare bank 1 and bank 2 sensor waveforms.
- Check fuel pressure — Verify both port and direct injection circuits.
Repair Costs
- O2/A-F sensor (bank 2): $120–$300
- Fuel injector: $140–$380
- Fuel pressure sensor/valve: $140–$330
- MAF sensor: $90–$230
Warranty Check
The 2021 Highlander should be within Toyota's 5-year/60,000-mile powertrain warranty. The basic warranty (3 years/36,000 miles) may have expired. O2 sensors are covered under the 8-year/80,000-mile federal emissions warranty. Contact your Toyota dealer.
Family SUV Considerations
The Highlander is a three-row family SUV that carries up to 8 passengers. P0175 isn't a safety concern, but a rich condition can cause rough running and reduced power that may be noticeable with a full load. Fix it within two weeks. The Highlander's V6 catalytic converters are expensive ($800-$1,800), so preventing catalyst damage from running rich is important.