Emissions

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

Severity: low Safe to drive

What P0158 means

The engine computer monitors the downstream (post-catalytic converter) oxygen sensor on Bank 2, Sensor 2. Its signal normally moves slowly and stays roughly between 0.1 and 0.9 V. P0158 sets when the voltage stays above the allowed limit, due to a bad sensor, a wiring short to voltage, or a truly rich exhaust.

Symptoms

  • Check Engine light on
  • Worse fuel economy
  • Rough or unstable idle
  • Fuel smell from the exhaust
  • Failed emissions test
  • Possible catalyst code P0430

Possible causes

  1. Failed Bank 2 Sensor 2 oxygen sensor
  2. Damaged wiring, short to voltage, or poor connector contact
  3. Rich air-fuel mixture on Bank 2 (injectors, fuel pressure)
  4. Exhaust leak near the sensor
  5. PCM input circuit fault (rare)

How to diagnose

  1. Scan for codes and freeze frame data, and note any misfire or fuel trim codes
  2. View live data for Bank 2 Sensor 2 and see whether the voltage is stuck high
  3. Check short- and long-term fuel trims on Bank 2; strongly negative values point to a rich mixture
  4. Inspect the sensor connector and harness for melting, chafing or corrosion
  5. Test the circuit for a short to voltage and confirm the sensor ground is good
  6. Look for exhaust leaks upstream of or near the sensor
  7. Check fuel pressure and injector condition if the mixture is rich
  8. If wiring and mixture are fine, replace the sensor and clear the code

Common fixes

  • Replace the Bank 2 Sensor 2 oxygen sensor
  • Repair the sensor wiring or connector
  • Fix exhaust leaks
  • Correct the cause of the rich mixture (injectors, fuel pressure regulator, sensors)
  • Diagnose or replace the PCM only after ruling out everything else

Questions and answers

Can I drive with a P0158 code?

Usually yes, for a short time. Fuel economy may suffer, and prolonged running rich can damage the catalytic converter.

What does Bank 2 Sensor 2 mean?

Bank 2 is the side of the engine that does not contain cylinder 1. Sensor 2 is the one after the catalytic converter, which monitors its efficiency.

Should I replace the sensor right away for P0158?

No. Check the wiring, connector, exhaust leaks and fuel trims first, because a rich mixture or a short circuit can cause the same code.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.