| DTC Data Sheet | |
| System | Powertrain |
| Standard | SAE J2012 / ISO 15031-6 |
| Fault type | Circuit Low |
| Official meaning | O2 Sensor Circuit Low Voltage (Bank 2, Sensor 1) |
The bank 2 upstream O2 sensor signal is stuck below the expected minimum, indicating either a permanently lean exhaust on bank 2 or a sensor reporting low.
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P0151 Quick Answer
The bank 2 upstream O2 sensor signal is stuck below the expected minimum, indicating either a permanently lean exhaust on bank 2 or a sensor reporting low.
What Does P0151 Mean?
O2 Sensor Circuit Low Voltage (Bank 2, Sensor 1). The bank 2 upstream O2 sensor signal is stuck below the expected minimum, indicating either a permanently lean exhaust on bank 2 or a sensor reporting low.
Symptoms
- Check engine light
- Lean misfires under load on bank 2
- Hesitation, rough idle
- Possible co-codes: P0171 / P0174
Common Causes
- Vacuum leak on bank 2 (most common cause of true lean)
- Bank 2 fuel injector clogged or under-delivering
- Bank 2 exhaust leak before the sensor
- Failed O2 sensor reading low
- Low fuel pressure
- Short to ground on the signal wire
Diagnosis Steps
You’ll need a scan tool capable of reading live powertrain data, a digital multimeter, and access to the wiring diagram for the specific platform.
- Read fuel trims for bank 2. STFT and LTFT positive (compensating for lean) confirm a real lean condition rather than a sensor fault.
- Smoke-test bank 2 intake for vacuum leaks.
- Check fuel pressure during the symptom event.
- Inspect bank 2 exhaust for cracks or leaking gaskets ahead of the sensor.
- Swap upstream sensors B1 and B2 — if the lean reading follows the sensor, replace it.
Possible Fixes
- Vacuum leak repair
- Fuel injector cleaning or replacement
- Exhaust leak repair
- O2 sensor replacement when proven faulty
Can I Still Drive With P0151?
The vehicle will usually still drive with P0151 stored, but performance, drivability, or emissions will be degraded. The PCM may inhibit emissions monitors and limit closed-loop fueling adjustments. Drive to a workshop, but don’t ignore the code long-term — degraded sensor data can mask other faults and shorten catalyst life.
How Serious Is This Code?
P0151 is a moderate-priority fault. It will not prevent the engine from running but unaddressed it can damage the catalytic converter, reduce fuel economy, or cause failed emissions testing. Address within a few drive cycles.
Brand-Specific Guides for P0151
Manufacturer-specific diagnostic procedures with factory data and pin-level details for vehicles where this code commonly sets:
FAQ
Will P0151 clear itself?
Only if the underlying fault was intermittent and self-corrected. Most root causes are persistent and require physical repair.
Can I clear P0151 without fixing it?
You can clear it with a scan tool, but it will return as soon as the fault condition reappears — typically within one or two drive cycles.
Is P0151 related to other codes?
Often, yes. Adjacent codes in the same circuit or system frequently set together — if P0151 is present, scan for related codes and address them as a group.