P0158 indicates that the downstream oxygen sensor on bank 2 (sensor 2) is reporting a voltage higher than the expected range. The engine control module interprets this as a circuit‑high condition, which can be caused by a faulty sensor, wiring shorted to power, or a poor connection.
The sensor’s internal signal circuit can drift high or the heater element can short, sending a voltage above the normal 0.1‑0.9 V range.
A damaged or chafed wire that contacts a power source forces the sensor signal line high.
Poor contact can create a high‑resistance path that the ECM reads as an elevated voltage.
Outside air entering the exhaust stream can cause the sensor to output a higher voltage than normal.
An internal driver or reference‑voltage problem in the control module could misinterpret the sensor signal, but this is uncommon.
Almost never. The code is most often caused by the sensor itself, wiring, or a connector issue. PCM replacement is only warranted after all other causes have been ruled out.
A failing catalyst does not directly cause a high‑voltage sensor circuit code. The code points to the sensor’s electrical signal, not catalyst efficiency.
Clearing the code only resets the light. If the underlying fault (sensor, wiring, leak) remains, the code will return.
Short‑term driving is usually safe, but the condition can reduce fuel economy, increase emissions, and may cause the vehicle to fail an emissions inspection.