What Does P0172 Mean on Your 2023 Toyota Highlander?
The 2023 Toyota Highlander received a major update, replacing the 3.5L V6 with a new 2.4L turbocharged inline-4 producing 265 hp in gas-only trims. Hybrid models continue with the 2.5L Atkinson-cycle engine paired with electric motors for 243 combined hp. P0172 means the ECM detected a rich condition on Bank 1. Both engines are inline-4 configurations, so Bank 1 covers all cylinders.
On a relatively new 2023 model, this code may be covered by Toyota's factory warranty. The new turbo engine may have specific calibration considerations that a dealer update can address.
Common Symptoms You Might Notice
- Check engine light on
- Fuel economy below the 22/29 MPG (turbo) or 36/35 MPG (hybrid) rating
- Faint fuel smell from exhaust
- Slightly rough idle
- Mild hesitation during acceleration
- Black deposits on tailpipe
Top Causes of P0172 on the 2023 Highlander
- MAF Sensor Issue (30% likelihood): The turbo engine's PCV system can introduce oil vapor to the MAF sensor. Even on a newer vehicle, contamination or a factory defect is possible.
- ECM Software Calibration (30% likelihood): The 2.4L turbo is relatively new in the Highlander. Toyota may have ECM updates that refine fuel delivery parameters.
- Faulty O2 Sensor (20% likelihood): A manufacturing defect in the upstream oxygen sensor can send incorrect data to the ECM.
- Turbo Intake or Boost Leak (20% likelihood): On the turbo model, loose intercooler piping or hose clamps can allow unmetered air that affects fuel calculations.
How to Diagnose P0172 on Your 2023 Highlander
- Check warranty coverage. The 2023 Highlander is covered by Toyota's 3-year/36,000-mile basic and 5-year/60,000-mile powertrain warranty.
- Ask about TSBs. Toyota may have issued Technical Service Bulletins for the new 2.4L turbo engine's fuel management.
- Inspect the air filter. Make sure it is properly seated and not excessively dirty.
- Check fuel trims if you have a scanner. Negative LTFT confirms a rich condition.
- On turbo models, check boost piping. Inspect intercooler hoses and clamps for tightness.
Repair Options and Costs
- Warranty repair: $0 at Toyota dealership
- MAF sensor cleaning: $10 DIY or $60-$110 at a shop
- MAF sensor replacement: $160-$310 parts and labor
- ECM software update: $0-$150 (usually warranty-covered)
- O2 sensor replacement: $180-$370 parts and labor
- Boost leak repair: $75-$300 depending on component
Can You DIY This Repair?
For a 2023 under warranty, visit the dealer first. If outside warranty, MAF sensor cleaning is straightforward. The new 2.4L turbo engine bay is well organized. Boost leak diagnosis requires more expertise and possibly a smoke machine. Leave ECM software updates to the dealer.
Prevention Tips
- Follow Toyota's maintenance schedule for the new turbo engine
- Use OEM air filters
- Do not modify the intake or turbo system
- Keep up with dealer software updates
- Use the recommended fuel grade (regular 87 octane for the turbo)