Emissions

P0145 — O2 Sensor Slow Response (Bank 1, Sensor 3)

Severity: low Safe to drive

What P0145 means

The engine control unit watches how quickly the signal from the Bank 1, Sensor 3 oxygen sensor changes, a sensor located after the main catalytic converter or at an additional exhaust stage. In a healthy system the voltage reacts quickly when exhaust gas content changes. If the switching is too sluggish, the ECU stores P0145 and turns on the check engine light. Sensor numbering varies by engine, so confirm the location for your vehicle.

Symptoms

  • Check engine light on
  • Slightly higher fuel consumption
  • Rough or unstable idle
  • Hesitation when accelerating
  • Failed emissions test

Possible causes

  1. Aged or contaminated Bank 1, Sensor 3 oxygen sensor
  2. Damaged, corroded or loose wiring or connector
  3. Faulty sensor heater circuit
  4. Exhaust leak near the sensor
  5. A failing catalytic converter changing the exhaust gas content
  6. Rarely, an ECU software or calibration problem

How to diagnose

  1. Scan all codes and freeze frame data and note any other oxygen sensor or fuel mixture codes
  2. Confirm from a diagram which sensor is Bank 1, Sensor 3 on this vehicle
  3. Inspect the connector and harness for melting, breaks, moisture and corroded pins
  4. Check the exhaust for leaks upstream of and around the sensor
  5. Watch the sensor signal and heater status in live data
  6. Review fuel trim values for mixture problems
  7. Test heater resistance and wire continuity to the ECU
  8. Clear the code after the repair and confirm it does not return

Common fixes

  • Replace the Bank 1, Sensor 3 oxygen sensor
  • Repair damaged wiring or replace the connector
  • Seal exhaust leaks near the sensor
  • Correct any fuel mixture problems found
  • Update the ECU software if the manufacturer offers it

Questions and answers

What does P0145 mean?

The control unit thinks the Bank 1, Sensor 3 oxygen sensor is reacting too slowly to changes in exhaust gas content. The sensor itself or its wiring is the most common culprit.

Can I drive with a P0145 code?

Usually yes, for a short time. Fuel use may go up and emissions control may be affected, so schedule a diagnosis soon.

Is replacing the sensor enough?

Not always. Check the wiring, connector and exhaust leaks first, otherwise a new sensor may set the same code again.

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.