What Does P0152 Mean?
The upstream O2 sensor on Bank 2 (Sensor 1) is reporting a persistently high voltage, indicating the sensor is reading a rich exhaust condition. The voltage remains above the expected threshold for longer than the PCM's calibrated time. This could indicate an actual rich-running condition on Bank 2 or a sensor/circuit fault biasing the signal high. The driver may notice black smoke from the exhaust, fuel smell, rough idle, and poor fuel economy.
Common Causes
30%
Leaking or stuck-open fuel injector on Bank 2 causing excessive fuel delivery
25%
Faulty O2 sensor stuck producing high voltage output
20%
High fuel pressure from a faulty fuel pressure regulator
15%
O2 sensor signal wire shorted to the heater voltage or battery voltage
10%
EVAP system purge valve stuck open flooding the engine with fuel vapor
Diagnostic Steps
1
Monitor Bank 2 Sensor 1 voltage — a stuck reading above 0.8V indicates either a real rich condition or a sensor/circuit fault; check STFT and LTFT for Bank 2 (large negative trims confirm actual rich running).
2
Disconnect the O2 sensor and check if the voltage drops to approximately 0.45V (bias voltage) — if it does, the sensor was responding to a real rich condition; if it stays high, the circuit or sensor is faulty.
3
Measure fuel pressure at the rail — pressures above specification (typically 35-65 psi) indicate a stuck fuel pressure regulator.
4
Perform an injector balance test or monitor individual cylinder fuel trim values — a leaking injector on Bank 2 will show as a negative fuel trim adjustment on that cylinder.
5
Inspect the EVAP purge valve by commanding it closed with a scan tool — if fuel trims normalize, the purge valve is stuck open and flooding the intake with fuel vapors.
Estimated Repair Cost
$100 - $500
Parts + labor, varies by vehicle and location
The upstream O2 sensor on Bank 2 (Sensor 1) is reporting a persistently high voltage, indicating the sensor is reading a rich exhaust condition. The voltage remains above the expected threshold for longer than the PCM's calibrated time. This could indicate an actual rich-running condition on Bank 2 ...
The most common cause of P0152 (Oxygen Sensor High Voltage, Engine Bank B, Upstream of Catalytic Converter) is: Leaking or stuck-open fuel injector on Bank 2 causing excessive fuel delivery
Typical repair costs for P0152 range from $100 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Drive with caution. A persistent rich condition can foul spark plugs, overheat the catalytic converter (risk of fire in extreme cases), and wash cylinder walls of oil leading to accelerated wear. Address promptly if black smoke or strong fuel smell is present.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0152 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel System / Emissions
Difficulty
Type
Generic (SAE)
Recommended Tools
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