P0170
Fuel Trim Bank 1
Fuel & air metering
Generic OBD-II
High
What it means
P0170 means the engine computer has had to correct fueling on bank 1 by more than it allows — the mixture is running too rich or too lean and the computer can't bring it back into range. It's usually a symptom of another problem: a vacuum leak, a dirty MAF, a weak fuel supply, or a failing oxygen sensor. It often shows up alongside a lean or rich code that points to the exact cause.
High
Can I keep driving? Usually drivable, but the engine may run rough or use extra fuel; fix it before a persistent rich or lean condition fouls plugs or the converter.
Common symptoms
What you'll notice
- Check-engine light on
- Poor fuel economy
- Rough idle or stalling
- Hesitation or reduced power
- Hard starting in some cases
Common causes
Most likely first
- Vacuum or intake leaks (lean condition)Likely
- Dirty or faulty MAF sensorCommon
- Faulty oxygen sensorCommon
- Fuel-delivery problems — clogged injectors or filter, weak pumpLess often
- Failing fuel pressure regulatorLess often
- Failed ECM (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and note the fuel-trim values and any partner codes (e.g. P0171 or P0172).
- Check for vacuum and intake leaks.
- Inspect the MAF sensor and clean it if dirty.
- Verify fuel pressure and check the oxygen sensor's switching.
- Inspect the injectors and fuel filter; suspect the ECM last.
FAQ
Quick answers
Is it safe to drive with P0170?+
Short trips are usually okay, but a large mixture error can cause stalling, misfires, and eventually converter damage. Get it diagnosed before it worsens.
Can I just clear P0170?+
It will return once the computer relearns fuel trims, because the underlying rich or lean condition is still there — usually a leak, a MAF, or a fuel-delivery issue.
Related codes
Often seen with P0170
Read & clear P0170 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX