What does OBD2 code P0172 mean?+
P0172 stands for System Too Rich Bank 1. Bank 1 is running too rich. The ECM is removing fuel but cannot get lean enough.
What causes code P0172?+
Leaking fuel injectors; Faulty coolant temp sensor causing over-fueling; Failing upstream O2 sensor stuck rich; Stuck-open fuel pressure regulator; Large vacuum leak causing lean code — opposite logic
How do I fix code P0172?+
Check for leaking fuel injectors (listen for ticking or test with noid light); Replace coolant temp sensor; Test O2 sensor switching; Check fuel pressure regulator; Inspect spark plugs for fouling
How much does it cost to fix P0172?+
Estimated repair cost for P0172 is $50–$500.
Is P0172 DIY-friendly?+
Yes — P0172 is generally DIY-friendly with basic tools.