P0172 — System too Rich (Bank 1)
Category: Powertrain Severity: Medium
Updated:
DTC code P0172 means: System too Rich (Bank 1). It falls under the "Powertrain" category, with an estimated severity of Medium. Common causes include faulty O2 sensor, leaking fuel injector and high fuel pressure; it's worth confirming the diagnosis before replacing parts.
Possible causes
- Faulty O2 sensor
- Leaking fuel injector
- High fuel pressure
- Faulty MAF sensor
- EVAP purge problem
Symptoms
- Loss of power when accelerating
- Unstable idle
- Higher fuel consumption
- Jerking while driving
How to diagnose it step by step
- Check the air filter.
- Clean or test the MAF sensor.
- Measure fuel pressure and check the regulator.
- Check for leaking injectors.
- Check the canister purge valve.
How to fix it
Clean or replace the MAF/MAP sensor and check for intake leaks.
Estimated repair cost
Air filter: $15–50. MAF: $100–300. Injector: $100–400.
Frequently asked questions
What does DTC code P0172 mean?
System too Rich (Bank 1).
Is code P0172 serious?
Severity Medium. Not urgent, but worth diagnosing to avoid bigger damage.
Can I keep driving with code P0172?
Yes, short term; a prolonged rich mixture damages the catalyst and spark plugs.
Related codes
P0171 P0174 P0175 P0161 P0157 P0156 P0155 P0190 P0153 P0191
Refine by car make
- Audi P0172: O2 sensor or fuel pressure.
- BMW P0172: Leaking injectors or O2 sensor.
- Citroën P0172: O2 sensor or injector.
- Dacia P0172: MAF/MAP sensor.
- Fiat P0172: O2 sensor or injector.
- Ford P0172: O2 sensor or leaking injector.
- Honda P0172: O2 sensor or injector.
- Hyundai P0172: O2 sensor or injector.
- Kia P0172: O2 sensor or injector.
- Mazda P0172: O2 sensor or injector.
- Mercedes-Benz P0172: Injectors or O2 sensor.
- Nissan P0172: O2 sensor or injector.
- Opel P0172: O2 sensor or injector.
- Peugeot P0172: O2 sensor or injector.
- Renault P0172: O2 sensor or injector.
- Toyota P0172: O2 sensor or injector.
- Volkswagen P0172: O2 sensor or fuel pressure regulator.
- Volvo P0172: MAF sensor.
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