P0170: Fuel Trim Bank 1
A generic powertrain (engine and transmission) trouble code, same meaning on every brand.
Yes with care - the engine is compensating for something, and the cause may grow.
Symptoms
- Rough idle
- Hesitation or surging
- Fuel economy noticeably off
Likely causes, most common first
- Vacuum leak on bank 1
- Mass air flow sensor reading low
- Fuel pressure too low or too high
- Leaking or clogged injectors
Read P0170 yourself before paying for diagnosis
A basic Bluetooth OBD-II scanner ($20-40) plugs into the port under the dashboard and shows this code with live sensor data on your phone - useful both for confirming the fix and for talking to a shop from an informed position.
What is going on and how it gets diagnosed
P0170 means the fuel trim on bank 1 has run out of adjustment room. The computer constantly nudges fuel delivery to keep the mixture correct; when the correction it needs exceeds roughly a quarter in either direction, it stops adjusting and reports this code.
The useful next step is reading the trim values rather than guessing. Positive trims mean the engine is being starved and the computer is adding fuel - look for unmetered air or weak fuel supply. Negative trims mean it is drowning and the computer is subtracting - look for leaking injectors, high fuel pressure, or a MAF reading too high.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Owner reports mentioning P0170
“Tl* the contact owns a 2003 infiniti g35. While driving between 45 and 60 mph, the vehicle shook violently while idling. The check engine light codes p0170 and p0174 illuminated. The vehicle was not diagnosed nor repaired. The VIN was not included in NHTSA campaign number: 03v455000 (engine and engine cooling). The manufacturer was notified of the failure. The failure mileage was 189,800.”2003 Infiniti G35 · Mar 2016 · 189,800 mi
Cars that report P0170 most often
Based on mentions of this code in NHTSA owner complaints.
Frequently asked questions
Can I drive with P0170?
Yes with care - the engine is compensating for something, and the cause may grow.
How much does it cost to fix P0170?
Typical US repair costs range from $20 for the simplest fix (vacuum leak repair) to $900 in the worst case. The right number depends on which cause your car has - see the causes list.
Related codes
The codes closest to P0170. They often appear together, and telling them apart is usually what narrows the diagnosis.
Definition per SAE J2012 standard nomenclature. Symptoms, causes and costs are editorial guidance - always confirm with a diagnosis of your specific vehicle.