What Does P0172 Mean on Your 2022 Infiniti QX80?
A P0172 code on your 2022 Infiniti QX80 means the ECM has detected that Bank 1 is running richer than the target air-fuel ratio. The 2022 QX80 features Nissan's VK56VD 5.6-liter naturally aspirated V8 engine producing 400 horsepower, paired with a 7-speed automatic transmission. Bank 1 is the driver-side cylinder bank on this engine.
The 5.6L V8 uses a dual injection system with both direct injection and port injection, similar to GM's approach. Running rich means excess fuel is entering the combustion chambers on Bank 1.
Symptoms You May Notice
- Check engine light on
- Fuel economy below the rated 14/20 mpg
- Rough or unsteady idle
- Black exhaust smoke
- Strong fuel smell from the exhaust
- Reduced power
- Misfires on Bank 1 cylinders
Common Causes of P0172 on the 2022 Infiniti QX80
- Dirty MAF Sensor - The mass airflow sensor on the 5.6L V8 can accumulate dust and oil contamination, causing inaccurate airflow readings and over-fueling.
- Leaking Fuel Injector on Bank 1 - With both port and direct injectors, either type can develop leaks. Port injectors are more prone to dripping on this engine.
- Faulty Bank 1 Upstream O2 Sensor - A degraded oxygen sensor provides incorrect data to the ECM, causing over-fueling.
- EVAP System Issue - A stuck-open purge valve can feed fuel vapors into the intake, enriching the mixture.
How to Diagnose P0172
- Scan all codes - Check for P0175 (Bank 2 rich), EVAP, MAF, and O2 companion codes.
- Review fuel trims - Compare Bank 1 and Bank 2 LTFT values. Bank 1 only being negative points to a bank-specific cause.
- Clean the MAF - The cheapest and easiest first step.
- Monitor O2 sensors - Check Bank 1 upstream sensor response.
- Test fuel injectors - Check both port and direct injectors on Bank 1.
- Test EVAP purge valve - Verify proper operation.
Repair Options and Cost Breakdown
- MAF Cleaning - $15-$30 DIY.
- MAF Replacement - $170-$380 parts and labor.
- Fuel Injector Replacement - $280-$600 per injector.
- O2 Sensor Replacement - $220-$430 parts and labor.
- EVAP Purge Valve - $90-$230 parts and labor.
Most P0172 repairs on the QX80 cost between $200 and $500. The QX80 is a premium full-size SUV, but the VK56 engine is well-established with good parts availability.
Can You DIY This Repair?
MAF cleaning is easy. The QX80 has a large, accessible engine bay that makes basic maintenance straightforward. O2 sensor replacement and purge valve replacement are possible DIY jobs. Fuel injector work on the dual injection system is more complex and best handled by a Nissan/Infiniti specialist.
Prevention Tips
- Replace the air filter every 15,000-20,000 miles
- Use quality 91+ octane fuel as recommended by Infiniti
- Add fuel system cleaner every 10,000 miles
- Follow the Infiniti maintenance schedule
- Address check engine lights promptly