P0152: OBD-II code P0152 means the upstream oxygen sensor on bank 2 is reading persistently high voltage — usually a real rich condition or a shorted sensor.

Symptoms

• Check engine light is on; bank 2 runs rich with black smoke, rough idle, and a raw fuel smell from the exhaust.
• Fuel economy drops noticeably and the bank 2 catalytic converter may overheat if left unresolved.
• The engine may misfire and foul spark plugs on bank 2 if the rich condition continues.

Common causes

• A failed bank 2 O2 sensor with an internally shorted signal element, pinned high.
• A stuck-open fuel injector on bank 2 or a leaking fuel pressure regulator causing a genuine rich condition.
• A short-to-voltage on the bank 2 O2 sensor signal wire between sensor and PCM.

What to do?

Read live bank 2 O2 voltage — if pinned around 0.9 V regardless of throttle, sensor is bad or a rich condition is real on that bank. Check bank 2 fuel trims. Unplug the sensor and confirm signal returns to 0.45 V reference. Replace the sensor or find the source of extra fuel.