P0175 Code on the 2024 Nissan Altima: Complete Diagnosis Guide
The 2024 Nissan Altima is equipped with the QR25DE 2.5L inline-four engine paired with Nissan's Xtronic CVT (continuously variable transmission). When your Altima throws a P0175 code, the engine control module (ECM) has determined that Bank 2 is running too rich. On an inline-four engine, the bank designation typically corresponds to the rear O2 sensor feedback zone, meaning the ECM's secondary fuel trim calculations are detecting excess fuel in the exhaust.
Symptoms of P0175 on the 2024 Altima
- Check engine light illuminated
- Reduced fuel economy below the expected 28-32 MPG city range
- Rough or slightly unstable idle
- Sluggish acceleration response
- Black residue inside the tailpipe
- Occasional stalling at stop lights in severe cases
Top Causes for the 2024 Altima
1. Contaminated Mass Airflow Sensor (High Likelihood)
The QR25DE engine's MAF sensor is positioned in the intake tube between the air filter and throttle body. Nissan's intake design is susceptible to oil vapor contamination from the PCV system, particularly as miles accumulate. A dirty MAF underreports airflow, causing the ECM to miscalculate fuel delivery. This is the most common and easiest-to-fix cause. Clean it with dedicated MAF sensor cleaner and check if the code returns after a few drive cycles.
2. Faulty Upstream Oxygen Sensor (Medium Likelihood)
The 2024 Altima uses air-fuel ratio sensors (wideband O2 sensors) for precise mixture control. If the upstream sensor on Bank 2 has degraded or is reading lean when the mixture is actually correct, the ECM will enrich the mixture unnecessarily. These sensors can degrade from exposure to silicone sealants, contaminated fuel, or simply from heat cycling. A scan tool capable of reading sensor voltage and response time is essential for diagnosis.
3. Leaking Fuel Injector (Medium Likelihood)
The QR25DE uses multi-port fuel injection with four injectors. If one or more injectors on the Bank 2 side are dribbling fuel when they should be closed, excess fuel enters the cylinders. This is more common at higher mileage but can occur on newer vehicles due to debris in the fuel system. An injector balance test or fuel pressure decay test can identify a leaker.
4. Fuel Pressure Regulator Sticking (Low Likelihood)
The fuel pressure regulator maintains consistent pressure to the fuel rail. If it sticks in a high-pressure position, all injectors deliver more fuel than commanded. On the 2024 Altima, the regulator is integrated into the fuel pump assembly. A fuel pressure gauge test at the rail will quickly confirm or rule out this cause.
CVT Interaction Note
Nissan's Xtronic CVT keeps the engine in specific RPM ranges for efficiency. When P0175 is active and the engine is running rich, the CVT's programming may hold higher RPMs to compensate for reduced power, further degrading fuel economy. Some owners report the CVT feeling sluggish or "hunting" for ratios when fuel mixture codes are present. Fixing the P0175 often resolves the perceived CVT behavior.
Diagnosis Steps
- Pull all codes with an OBD-II scanner. Check for related codes like P0172, P0101, or P0113.
- Review freeze frame data to understand the conditions when the code set.
- Check fuel trim values. LTFT negative values exceeding -8% to -10% confirm a rich condition.
- Clean the MAF sensor as a first step. Use only MAF-safe cleaner.
- Monitor the upstream O2/AFR sensor with a scan tool. Look for lazy response or bias.
- If needed, perform fuel pressure testing and injector balance tests.
Repair Costs
MAF cleaning costs $10-$15 for spray cleaner. MAF sensor replacement is $120-$280. Upstream O2 sensor replacement runs $180-$350 for parts and labor. Fuel injector replacement costs $150-$350 per injector on the QR25DE. Fuel pressure regulator/pump assembly replacement can range from $400-$700. Diagnostic fees typically run $80-$140 at independent shops.