P0150: O2 Sensor Circuit Malfunction (Bank 2, Sensor 1) (Meaning, Causes, Fixes)
What P0150 means
Sensor 1 is the upstream oxygen sensor, the first one downstream of the engine on bank 2. Bank 2 only exists on engines with two cylinder banks, such as V6 and V8 engines; it is the side that does not have cylinder 1. The engine computer uses this sensor's signal to decide how much fuel to inject. OBD-Codes.com explains that the sensor produces about 0.1 volts when the exhaust is lean and about 0.9 volts when it is rich, and that P0150 sets in closed loop when the voltage stays below about 0.4 volts for too long (more than 20 seconds is a typical figure, but it varies by model). RepairPal describes it more broadly: the bank 2 sensor 1 signal 'is not within the proper voltage limits', set when the PCM detects a failure of the sensor or of the information it sends. The sources also differ on the likely result: OBD-Codes.com describes a low (lean) signal, while RepairPal says the engine may start to run too rich.
Severity: can I keep driving?
Usually OK to drive
Get it checked within a reasonable time. RepairPal rates P0150 'Moderate', meaning it isn't usually an immediate safety risk, and OBD-Codes.com says an intermittent fault may cause nothing more than the check engine light. Left alone, though, RepairPal warns the engine can run too rich and damage other parts, and it can hurt fuel economy and cause an emissions test failure. If the check engine light is flashing, the engine stalls or runs very rough, or you smell fuel or see heavy black smoke, stop driving and have it looked at. Exhaust parts get very hot, so let the car cool fully before touching the oxygen sensor.
Common symptoms
- Check engine light on
- Engine runs rough, misses or stumbles
- Engine running rich, which RepairPal says can foul the spark plugs and cause misfires
- Poorer fuel economy
- Black smoke from the tailpipe
- Engine stalls (dies)
- Sometimes no other symptoms, especially if the fault is intermittent (per OBD-Codes.com)
Likely causes
Roughly most to least common, based on the sources below. Your vehicle may differ.
- Faulty bank 2 sensor 1 oxygen sensor (the usual cause, especially if the sensor is old, per OBD-Codes.com)
- Water, corrosion or loose terminals in the sensor connector
- Wiring burnt on exhaust parts, or an open or short from wiring rubbing on engine components
- Exhaust leak near the sensor, such as at the manifold or where it joins the header pipe (both sources)
- Unmetered vacuum leak at the engine
- Faulty PCM (less likely)
Diagnostic steps you can do
Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.
- Read all stored codes. Lean, misfire or vacuum leak codes alongside P0150 point to a leak or fuel problem rather than the sensor itself.
- With the exhaust cold, find the bank 2 sensor 1 oxygen sensor ahead of the catalytic converter on the side of the engine without cylinder 1, and check its wiring and connector for water, corrosion, loose pins, burns or chafing.
- Look and listen for exhaust leaks at the bank 2 exhaust manifold and header pipe, and for vacuum leaks at the engine, such as hissing hoses or ticking at a cold start.
- Clean corrosion from the connector and make sure it is fully seated.
- Clear the code and drive normally. If it comes back, the sensor or its circuit needs testing (see below).
Typical fixes
- Replace the bank 2 sensor 1 oxygen sensor
- Repair damaged, burnt or chafed wiring, or a corroded or loose connector
- Repair an exhaust leak near the sensor
- Fix a vacuum or intake air leak
- Replace the PCM only after the sensor and wiring are confirmed good
Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.
🛠 When to call a pro
- OBD-Codes.com recommends watching the bank 2 sensor 1 on a scan tool. It should switch quickly and evenly between rich and lean. If it does, look for an intermittent wiring fault with a wiggle test while watching the voltage.
- If it doesn't switch properly, OBD-Codes.com describes briefly forcing a rich condition and then a lean one to see if the sensor reacts. A sensor that reacts correctly suggests an exhaust hole or vacuum leak instead of a bad sensor.
- A sluggish or dead sensor calls for checking the 5-volt reference, the 12-volt heater supply and the ground circuit with the sensor unplugged, then replacing the sensor if all are correct (per OBD-Codes.com).
- The sources describe the fault differently: OBD-Codes.com describes a low, lean-reading signal, while RepairPal says the voltage is out of limits and the engine may run rich. A shop can sort this out with live data and a wiring diagram.
- The code returns after a new sensor, or other fuel trim or misfire codes are also present
Where to buy
Plain search links. Always match parts to your exact year, make, model and engine.
FAQs
Can I drive with P0150?
Usually, for a while. RepairPal rates it 'Moderate'. Get it diagnosed within a reasonable time, because it can make the engine run rough or rich, cut fuel economy and fail an emissions test. Stop driving if the check engine light flashes or the engine stalls.
Which oxygen sensor is bank 2 sensor 1?
It is the sensor before the catalytic converter on bank 2, the side of a V6 or V8 engine that does not have cylinder 1. Four-cylinder and inline engines with one exhaust bank don't have a bank 2.
What's the difference between P0150 and P0130?
They describe the same oxygen sensor circuit fault on opposite sides of the engine. P0130 is for bank 1 sensor 1 and P0150 is for bank 2 sensor 1.
Will replacing the oxygen sensor fix P0150?
Often. OBD-Codes.com says a bad sensor is the usual cause, especially if it is old. Check the wiring, connector and for exhaust or vacuum leaks first, since both sources list leaks as possible causes too.
Sources
Last reviewed 2026-10-24. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.