P0172
System Too Rich Bank 1
Powertrain · Generic (all makes)System: Fuel Delivery + Emissions
Fix within days. Damage or fuel waste builds up.
Likely causes
- Leaking fuel injector
- Fuel pressure regulator stuck closed
- Contaminated mass air flow sensor
- Faulty front oxygen sensor
What to check first
Check fuel pressure and look for a leaking injector or a regulator diaphragm leaking fuel into the vacuum line.
Typical repair cost
$100 – $600
Independent-shop parts and labor for the usual fix. Your price depends on the actual cause and the vehicle.
Next step
General information, not a diagnosis of your vehicle. Repair costs are typical shop ranges, not quotes.