Emissions

P0163 — O2 Sensor Circuit Low Voltage (Bank 2, Sensor 3)

Severity: low Safe to drive

What P0163 means

The engine computer monitors the signal from the oxygen sensor in the Bank 2, Sensor 3 position, typically located after the main or a secondary catalytic converter. P0163 sets when the circuit voltage stays below the expected range. Causes include a failed sensor, an open or shorted-to-ground wire, or an exhaust leak. Sensor numbering varies by vehicle, so confirm the location for your model.

Symptoms

  • Check Engine light on
  • Reduced fuel economy
  • Rough or unstable idle
  • Hesitation during acceleration
  • Failed emissions test

Possible causes

  1. Failed Bank 2 Sensor 3 oxygen sensor
  2. Damaged, corroded or broken wiring or connector
  3. Signal wire shorted to ground
  4. Exhaust leak near or ahead of the sensor
  5. ECM sensor circuit fault (rare)

How to diagnose

  1. Scan all codes and review freeze frame data, noting any other O2 sensor codes
  2. Confirm which sensor is Bank 2, Sensor 3 on your vehicle
  3. Inspect the wiring and connector for chafing, heat damage and corrosion
  4. Watch live data for sensor voltage and heater status
  5. Check the exhaust for leaks near and ahead of the sensor
  6. Review fuel trims to rule out a mixture problem
  7. Test wires for continuity and shorts to ground, and check sensor power and heater circuit if needed

Common fixes

  • Replace the Bank 2 Sensor 3 oxygen sensor
  • Repair the wiring or replace the connector
  • Fix the exhaust leak
  • Replace or reprogram the ECM only after everything else is ruled out

Questions and answers

What does P0163 mean?

The ECM detected low voltage in the oxygen sensor circuit for Bank 2, Sensor 3. The sensor or its wiring is the most common cause.

Can I drive with P0163?

Usually yes for a short time. It is still best to repair it to protect fuel economy and pass emissions testing.

Will clearing the code fix it?

Only temporarily. If the cause remains, the code returns and the light comes back on.

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.