P0151: O2 Sensor Circuit Low Voltage Bank 2 Sensor 1
A generic powertrain (engine and transmission) trouble code, same meaning on every brand.
Yes briefly - the computer will add fuel in response and economy will suffer.
Symptoms
- Poor fuel economy
- Rough running on one bank
- Emissions test failure
Likely causes, most common first
- Bank 2 upstream sensor signal shorted to ground
- Failed sensor
- Exhaust leak upstream of the sensor
- Wiring damaged by exhaust heat
Read P0151 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
P0151 is a low-voltage fault on the bank 2 upstream sensor, which the computer reads as a permanently lean mixture. Its response is to add fuel to a bank that may not need it, so economy drops and the exhaust smells rich even though the code says lean.
Bank 2 codes only exist on engines with two cylinder banks. Since bank 2 is the side without cylinder 1, and manufacturers do not agree on which physical side that is, confirm the numbering for your engine before working on the wrong sensor - they are frequently the same part number and easy to mix up.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Cars that report P0151 most often
Based on mentions of this code in NHTSA owner complaints.
Frequently asked questions
Can I drive with P0151?
Yes briefly - the computer will add fuel in response and economy will suffer.
How much does it cost to fix P0151?
Typical US repair costs range from $80 for the simplest fix (upstream oxygen sensor) 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 P0151. 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.