What Does P0172 Mean on Your 2022 Lexus ES?
A P0172 code on your 2022 Lexus ES tells you the engine control module has detected a rich fuel condition on Bank 1. The 2022 ES is available with three powertrains: the ES 250 with a 2.5L A25A-FKS four-cylinder (203 hp), the ES 350 with a 3.5L 2GR-FKS V6 (302 hp), and the ES 300h hybrid with a 2.5L four-cylinder paired with an electric motor.
On the four-cylinder models (ES 250 and ES 300h), Bank 1 is the only bank since it's an inline engine. On the ES 350 V6, Bank 1 is the front bank closest to the radiator. Regardless of trim, the diagnostic approach is similar.
Symptoms You Might Notice
- Check engine light illuminated
- Noticeably worse fuel economy
- Rough or slightly unstable idle
- Fuel odor from the tailpipe
- Black soot on exhaust tips
- Occasional misfires or hesitation
Common Causes of P0172 on the 2022 Lexus ES
- Contaminated MAF Sensor — The mass airflow sensor reads incoming air volume. Contamination from dust, oil, or aftermarket filter residue causes under-reading, prompting the ECM to inject too much fuel.
- Failing Upstream O2 Sensor — The Bank 1 Sensor 1 oxygen sensor may be sluggish or giving a biased reading, causing the ECM to maintain an excessively rich mixture.
- EVAP Purge Valve Stuck Open — When the canister purge solenoid fails in the open position, it continuously feeds fuel vapors into the intake, creating an unintended rich condition.
- Worn or Leaking Fuel Injector — An injector that drips or doesn't fully close adds unmetered fuel to the cylinder, especially noticeable at idle.
How to Diagnose the Problem
- Scan for all DTCs — Check for related codes on both banks (V6) or supplemental codes on the I4.
- Review fuel trim data — LTFT values more negative than -10% confirm the rich condition.
- Inspect and test the MAF sensor — Compare grams-per-second readings against Toyota specifications at idle and under load.
- Monitor O2 sensor waveform — Look for proper 0.1V-0.9V switching at the correct frequency.
- Test the purge valve — Use bidirectional control to verify it opens and closes on command.
- Perform injector balance test — Check that all injectors contribute evenly to engine RPM.
Repair Options and Cost Estimates
The 2022 Lexus ES is a luxury sedan, so expect premium pricing at the dealer. Independent shops with Toyota/Lexus experience offer good value for out-of-warranty work.
- MAF Sensor Cleaning — DIY: $8-$12. Shop: $75-$140.
- MAF Sensor Replacement — Parts: $110-$240, labor: $75-$140. Total: $185-$380.
- O2 Sensor Replacement — Parts: $130-$280, labor: $100-$180. Total: $230-$460.
- EVAP Purge Valve Replacement — Parts: $35-$90, labor: $70-$130. Total: $105-$220.
- Fuel Injector Replacement — Parts: $70-$160 each, labor: $180-$350. Total: $250-$510 per injector.
Can You Fix This Yourself?
MAF sensor cleaning is a beginner-friendly DIY job that takes about 10 minutes. O2 sensor replacement is doable with basic tools and a jack. Injector replacement on the ES 350 V6 requires removing the intake manifold and is best left to professionals. The ES 250 four-cylinder has easier injector access.
Prevention Tips
- Replace the engine air filter every 15,000-20,000 miles
- Use top-tier gasoline (87 octane minimum, premium preferred)
- Follow the Lexus maintenance schedule
- Avoid oiled aftermarket air filters
- Address any drivability changes or warning lights promptly