What Does P0172 Mean on Your 2024 Nissan Altima?
A P0172 code on the 2024 Nissan Altima means the engine control module has detected that Bank 1 is running too rich. The 2024 Altima is powered by a 2.5L naturally aspirated four-cylinder engine (QR25DE) producing 188 horsepower. As an inline-four, there is only one bank, so P0172 affects the entire engine's fuel mixture.
Running rich means the fuel system is delivering more fuel than the optimal 14.7:1 air-to-fuel ratio. This reduces fuel economy, can foul spark plugs, and stresses the catalytic converter. Since the 2024 Altima is under warranty, take advantage of dealer service.
Common Symptoms You May Notice
- Check engine light on
- Reduced fuel economy
- Rough or unsteady idle
- Black exhaust smoke
- Fuel smell from the tailpipe
- Hesitation during acceleration
Top Causes of P0172 on the 2024 Altima
- Dirty MAF sensor - The mass airflow sensor is the most common cause of P0172 on Nissan vehicles. Contamination causes underreported airflow and excess fueling.
- Faulty upstream O2 sensor - A defective oxygen sensor can cause incorrect fuel trim calculations, even on a new vehicle.
- Leaking fuel injector - A fuel injector that does not close properly delivers excess fuel to the cylinder.
- EVAP purge valve stuck open - A malfunctioning purge valve allows fuel vapors to flood the intake manifold.
How to Diagnose the Problem
Scan for codes and review freeze frame data. Check STFT and LTFT values. Negative LTFT past -10% confirms the rich condition.
Clean the MAF sensor with dedicated MAF cleaner spray. On the Altima, the MAF is located in the air intake tube between the air filter box and the throttle body. Monitor the upstream O2 sensor with live data; it should oscillate between 0.1V and 0.9V.
Repair Options and Cost Estimates
- MAF sensor cleaning or replacement: Cleaning under $10. New sensor $40-$130 plus $35-$80 labor.
- O2 sensor replacement: Parts $40-$130. Labor $55-$115.
- Fuel injector replacement: Parts $30-$80 per injector. Labor $130-$280.
- EVAP purge valve: Parts $20-$50. Labor $40-$85.
Can You Fix This Yourself?
MAF cleaning is easy on the Altima. O2 sensor replacement is moderate. Since the 2024 model is under warranty, dealer service is recommended.
Prevention Tips
- Follow the factory maintenance schedule
- Use quality fuel from reputable stations
- Address check engine lights promptly
- Keep maintenance records for warranty purposes