P0152
O2 Sensor Circuit High Voltage (Bank 2, Sensor 1)
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The P0152 code indicates that the upstream oxygen sensor on Bank 2 is outputting a voltage that is persistently higher than normal. High voltage from an O2 sensor (near or above 0.9V) tells the PCM that the exhaust is running rich — meaning there is excess fuel and insufficient oxygen. When this reading is continuous rather than cycling normally, the PCM triggers this code.
Because the upstream sensor directly controls fuel delivery for Bank 2, a stuck-high reading can cause the PCM to reduce fuel delivery to compensate. This can lead to a variety of drivability issues. Paradoxically, if the engine really is running rich, you may see black smoke from the exhaust, poor fuel economy, and a strong fuel smell. If the sensor is falsely reading high, the PCM's compensation could cause lean misfires.
Diagnosis should determine whether the sensor is accurately reading a rich condition or is producing a false signal. Check the sensor's wiring for shorts to power. If the wiring is fine, swap or test the sensor. If the new sensor also reads high, investigate fuel system issues on Bank 2 such as leaking injectors or a faulty fuel pressure regulator. Also check for oil or coolant contamination that could affect sensor readings.
Severity
Symptoms
- •Check engine light is on
- •Engine runs rich on Bank 2
- •Increased fuel consumption
- •Black smoke from the exhaust
- •Strong fuel smell from exhaust
- •Rough idle or engine misfires
Likely Causes
The oxygen sensor has failed in a way that its output voltage is stuck high, falsely indicating a constant rich exhaust condition to the PCM.
A wiring fault where the signal wire has shorted to a power source forces the voltage reading to stay high regardless of actual exhaust conditions.
Leaking fuel injectors, a faulty fuel pressure regulator, or a stuck-open purge valve can cause genuine over-fueling that the sensor is accurately detecting.
Oil or fuel contamination from worn valve seals, piston rings, or a PCV system issue can coat the sensor and cause it to read artificially high.
An internal coolant leak can introduce combustion byproducts that affect the sensor reading and cause a persistent high-voltage output.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Replace the upstream O2 sensor (Bank 2, Sensor 1)
- Repair short circuits in the sensor signal wiring
- Diagnose and fix fuel system issues causing a rich condition
- Address oil consumption or leak issues contaminating the sensor
- Check for head gasket leaks if coolant contamination is suspected