P0172Medium urgency

System Too Rich (Bank 1)

Fuel System · Air/Fuel Mixture

⚠️ Drive with caution — rich conditions can foul spark plugs.

What this means

Bank 1 is running rich — too much fuel relative to air. The ECU is hitting its correction limits. Common causes: stuck-open fuel injector, faulty MAF sensor, or leaking fuel pressure regulator.

Likely causes

Faulty or dirty MAF sensorMost common
Stuck-open fuel injectorCommon
Fuel pressure regulator failureCommon

Estimated repair cost

MAF sensor cleaning/replace$100 – $300

Fuel injector service$150 – $400

Fuel pressure regulator$150 – $350

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Frequently asked questions

What does P0172 mean?

Bank 1 is running rich — too much fuel relative to air. The ECU is hitting its correction limits. Common causes: stuck-open fuel injector, faulty MAF sensor, or leaking fuel pressure regulator.

Is P0172 serious?

Drive with caution — rich conditions can foul spark plugs.

How much does it cost to fix P0172?

Repair costs for P0172 range from $100 – $300 depending on the root cause and your vehicle.

Can I drive with P0172?

You can drive short distances but should have it repaired within 1-2 weeks to prevent further damage.