What P0151 means
The oxygen sensor before the catalytic converter on bank 2 (sensor 1) is the main control sensor for the mixture.
How the engine computer detects it
It is either a switching sensor (about 0.1 V lean to 0.9 V rich) or a wide-band sensor that works with a pump current evaluated by an interface chip. Bank 2 exists only on engines with two exhaust manifolds. P0151 is the bank 2 counterpart of P0131. On switching sensors the signal stays below about 40–50 mV in closed loop with a stoichiometric target (GM LT4: 285 of 350 samples; GM 3.0/3.6 V6 within 50 s); on wide-band sensors the interface chip reports a sensor wire shorted to ground. Two trips. A genuinely lean bank 2 shows up as P0174 rather than this code. A stored code usually switches mixture control to open loop and suspends adaptation and converter monitoring.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light on
- Higher consumption, possibly rough running (no mixture control)
- Higher emissions, possible emissions test failure
- Possibly with P0174/P2197
Common causes
- Signal wire (or a wide-band sensor wire) shorted to ground, e.g. chafed on exhaust or transmission Most likely
- Sensor faulty or poisoned (permanently lean signal) Most likely
- Large exhaust leak ahead of the sensor or misfires Possible
- Connector wet or corroded Possible
How to diagnose P0151
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: oxygen sensor bank2 sensor1, oxygen sensor wiring, engine control module.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 1
- Fuel and air metering
- 51
- Specific fault
Questions drivers ask
Can I drive with code P0151?
Usually yes for a short time, if the car drives normally, the temperature gauge reads normal and the check engine light is steady. If the light flashes, the engine loses power or overheats, or other warning lights come on, pull over and have it checked.
Will my car pass an emissions inspection with P0151?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Will P0151 clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
Can I fix P0151 myself?
Often yes, with an OBD-II scanner and basic tools. Difficulty: medium. Start with the cheapest checks before replacing expensive parts.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.