P0100 on Your 2021 Toyota Highlander
A P0100 code on your 2021 Toyota Highlander indicates the ECM has detected a malfunction in the mass air flow (MAF) sensor circuit. Your 4th-generation Highlander uses either the 3.5L V6 or the 2.5L hybrid powertrain, both depending on accurate MAF readings for fuel control.
Symptoms
- Check engine light on
- Rough or unstable idle
- Hesitation during acceleration
- Reduced power—especially noticeable loaded
- Poor fuel economy
- Possible stalling
Common Causes
- Contaminated MAF sensor (35%) — Oil, dirt, or debris accumulating on the sensing element after four-plus years.
- Wiring or connector issues (22%) — Heat and vibration affecting connections.
- Faulty MAF sensor (18%) — Internal sensor failure.
- Intake air leak (13%) — Cracked boot or loose clamp.
- Air filter restriction (8%) — Overdue filter change.
- ECM issue (4%) — Rare.
Diagnostic Steps
- MAF sensor cleaning — Remove and clean with dedicated MAF cleaner spray.
- Connector inspection — Check for corrosion and looseness.
- Air filter replacement — Fresh OEM-style paper filter.
- Intake inspection — Check all post-MAF connections.
- Scan tool data — Verify MAF readings at idle and under load.
- MAF replacement — If cleaning doesn't resolve the code.
Repair Costs
- MAF cleaning: $10–$15 (DIY)
- Air filter: $15–$28 (DIY)
- MAF sensor (V6): $145–$340
- MAF sensor (hybrid): $135–$310
- Intake boot: $75–$195
- Wiring repair: $90–$270
Warranty
Your 2021 Highlander's basic warranty has expired. The federal emissions warranty covers the MAF sensor for 8 years/80,000 miles through 2029. Check mileage with your Toyota dealer.