P0158: O2 Sensor Circuit High Voltage (Bank 2 Sensor 2)

What it means

The ECU detects a high voltage signal from the downstream oxygen sensor on bank 2.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

Bank 2 sensor 2 measures oxygen in the exhaust after the bank 2 catalytic converter. P0158 sets when the ECU sees an unusually high voltage from this downstream sensor; the cause may be a rich exhaust reading or a sensor or circuit fault producing a high signal.

Common causes

Most likely first.

1. Lean condition on bank 2
2. O2 sensor failed
3. Connector pins corroded - high contact resistance

Symptoms

• Check engine light on
• Increased fuel consumption
• Possible rough idle or hesitation
• Failed emissions test

How to diagnose it

1. Save freeze-frame data and compare warm live data from bank 2 sensor 2 with bank 1 sensor 2 to confirm that the high reading is persistent.
2. Inspect the downstream bank 2 sensor connector and wiring for corrosion, pushed-back pins, heat damage, or a signal wire shorted to voltage.
3. Check bank 2 fuel trims, misfire data, and upstream sensor behavior for evidence of a genuinely rich condition.
4. Test the downstream signal circuit for shorts and poor connections, following the wiring diagram and manufacturer’s specification.
5. If the mixture and circuit check out, test bank 2 sensor 2 response and replace it only if it fails.

Common fixes

• Repair corroded or loose connector terminals at bank 2 sensor 2.
• Repair a signal wire short to voltage or heat-damaged wiring.
• Correct a confirmed rich-running fault affecting bank 2.
• Replace bank 2 sensor 2 if it continues to report high voltage with a sound circuit and normal mixture.

Can I keep driving?

With a steady light, a short gentle drive is generally possible, but continued rich running can increase fuel use and damage the catalytic converter. Avoid hard acceleration and stop if the light flashes or the engine runs badly.