P0173: Fuel Trim Bank 2
A generic powertrain (engine and transmission) trouble code, same meaning on every brand.
Yes with care - same reasoning as P0170, on the other bank.
Symptoms
- Uneven idle
- Loss of power
- Poor economy
Likely causes, most common first
- Vacuum leak on bank 2
- Fuel supply problem affecting that bank
- Oxygen sensor on bank 2 misreporting
- Injector fault on bank 2
Read P0173 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
P0173 is the bank 2 version of a fuel trim limit. Because the two banks share a fuel pump, a filter and an air filter, a problem in any shared component normally sets trim codes on both banks at once.
That symmetry is the diagnostic shortcut. One bank alone in trouble points to something local to that bank - a cracked intake runner, one bad sensor, one leaking injector. Both banks together points to something common: fuel pressure, the air metering system, or a large vacuum leak at the throttle body or brake booster.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Owner reports mentioning P0173
“Vehicle started making a whining noise and eventually would not accelerate. Vehicle coasted to a stop on the side of the road where it had to be towed. It was checked by computer and the code p0173 came up (transmission failure). *la”2002 Honda Civic · Jan 2004 · 52,300 mi
Cars that report P0173 most often
Based on mentions of this code in NHTSA owner complaints.
Frequently asked questions
Can I drive with P0173?
Yes with care - same reasoning as P0170, on the other bank.
How much does it cost to fix P0173?
Typical US repair costs range from $100 for the simplest fix (vacuum leak repair) to $600 in the worst case. The right number depends on which cause your car has - see the causes list.
Related codes
The codes closest to P0173. 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.