P0151
Medium SeverityO2 Sensor Circuit Low Voltage (Bank 2, Sensor 1)
Emissions System
P0151 — Instant Answer
O2 Sensor Circuit Low Voltage (Bank 2, Sensor 1)
Severity: MEDIUM SEVERITY
Meaning: Upstream O2 sensor on bank 2 is stuck low, reading lean.
Safe to drive? Usually yes with caution, but confirm root cause before long trips.
Estimated repair cost: $30 - $100
Most common causes:
- 1. Failed O2 sensor (35-45% of cases)
- 2. Vacuum leak on bank 2 (10-25% of cases)
- 3. Exhaust leak near sensor (10-25% of cases)
Common Causes
How to Diagnose P0151
- 1Check for vacuum leaks on bank 2 side
- 2Monitor sensor voltage
- 3Check fuel trim for bank 2
- 4Replace sensor if stuck
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Related Resources
Repair guides, symptom pages, and wiring diagrams related to P0151.
Related Symptoms
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Related Codes
General fault with the upstream O2 sensor on bank 2 of a V-engine.
Same as P0171 but on bank 2. If both P0171 and P0174 are present, the issue is likely shared (MAF, fuel pump, or large vacuum leak).
Upstream O2 sensor bank 2 reads too high (rich).
Frequently Asked Questions
- Why only bank 2?
- If only bank 2 is lean, the issue is likely specific to that side — a vacuum leak, exhaust leak, or bad sensor on that bank.
- Can I swap bank 1 and bank 2 sensors to test?
- Yes — if the code follows the sensor, the sensor is bad. If it stays on bank 2, the problem is something else.
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Author & Review
Written by AllOEMManuals Editorial Team. Reviewed by ASE-certified technicians and updated with factory-reference checks for fitment-sensitive steps.
This guide was drafted with AI assistance and reviewed for accuracy by a human editor.
Last updated: 2026-05-07