What does code P0172 mean on a Nissan and is it safe to drive?
P0172: System Too Rich (Bank 1). Here's what it means on your Nissan, what usually causes it, what repairs typically cost, and how safe it is to keep driving.
PowertrainMedium urgency
What this code means
Too much fuel relative to air. O2 sensor detects low oxygen in exhaust; PCM is reducing fuel trim.
Common causes for your Nissan
- Faulty MAF or O2 sensor
- Leaking fuel injector(s)
- High fuel pressure
- Faulty purge valve stuck open
Symptoms
- Check Engine Light
- Rich smell, black smoke
- Poor fuel economy
- Rough idle possible
Typical fixes
- Replace MAF or O2 sensor
- Test fuel pressure and injectors
- Replace purge valve if stuck open
Repair cost range
For a Nissan, repairs for P0172 often fall between $100 and $600, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.
Known issues on Nissan
Nissan P0172 on QR25DE and VQ35DE engines often points to a faulty upstream O2 sensor or a leaking fuel injector. Check for a rich fuel smell from the oil dipstick, which indicates injectors leaking at rest.
Most commonly affected models
Altima 2002–2012Sentra 2007–2012Frontier 2001–2012