The 2022 Infiniti Q50's VR30DDTT twin-turbo V6 delivers exhilarating performance—until a check engine light accompanied by noticeable power loss appears. When P0172 (System Too Rich Bank 1) is stored, the engine is receiving too much fuel relative to air, and the computer is limiting performance to protect the catalytic converters.
Understanding P0172
Code P0172 indicates the engine control module detects a rich condition on bank 1—too much fuel for the amount of air entering the engine. The VR30's twin-turbo system adds complexity to air-fuel management, with multiple sensors and control systems involved.
Why Power Loss Occurs
When the engine runs rich, the ECU reduces power to prevent catalyst damage and excessive fuel consumption. This protective measure is why you feel the car is down on power—it's limiting itself intentionally.
Symptoms You're Experiencing
- Check engine light illuminated
- Noticeable loss of acceleration
- Possible rough idle
- Black smoke from exhaust under acceleration
- Strong fuel smell
- Decreased fuel economy
- Possible sluggish throttle response
Primary Causes
Oxygen Sensor Failure
The upstream O2 sensor on bank 1 may be reporting incorrect readings, causing the ECU to add fuel unnecessarily. Sensor failure is common on higher-mileage vehicles.
MAF Sensor Issues
A dirty or failing mass airflow sensor may over-report air entering the engine, causing excess fuel injection.
Fuel Pressure Regulator Stuck
If the fuel pressure regulator fails in the open position, excess fuel floods the system.
Leaking Fuel Injectors
Injectors that leak when closed allow fuel to enter cylinders constantly, enriching the mixture.
EVAP System Problems
A stuck-open purge valve can dump fuel vapor into the intake, enriching the mixture.
Repair Costs
| Repair | Parts | Labor | Total |
|---|---|---|---|
| Oxygen sensor (Bank 1) | $150-$300 | $100-$200 | $250-$500 |
| MAF sensor replacement | $150-$300 | $75-$150 | $225-$450 |
| Fuel pressure regulator | $100-$250 | $150-$300 | $250-$550 |
| Fuel injector (single) | $150-$300 | $200-$350 | $350-$650 |
Diagnostic Priority
Fuel trim data from a quality scan tool reveals whether the rich condition is real or sensor-reported. Long-term fuel trim significantly negative indicates the computer is actively reducing fuel to compensate for detected richness.