Emissions

P019D — O2 Sensor Delayed Response, Lean to Rich (Bank 2 Sensor 3)

Severity: low Safe to drive

What P019D means

The engine control unit (ECU) watches how quickly the Bank 2 Sensor 3 oxygen sensor, usually located downstream of the catalytic converter or farther back in the exhaust, responds when the mixture shifts from lean to rich. A healthy sensor switches fast. If the change is delayed, the ECU stores P019D and turns on the Check Engine light. The exact sensor location depends on the vehicle's exhaust layout.

Symptoms

  • Check Engine light on
  • Reduced fuel economy
  • Rough or unstable idle
  • Hesitation or reduced power
  • Increased emissions
  • Sometimes no symptoms besides the light

Possible causes

  1. Aged or contaminated Bank 2 Sensor 3 oxygen sensor
  2. Damaged wiring or a poor connection at the sensor connector
  3. Sensor heater circuit fault
  4. Exhaust leak near the sensor
  5. Mixture problem upstream (vacuum leak, injectors, fuel pressure)
  6. Failing catalytic converter skewing the readings

How to diagnose

  1. Scan all codes and freeze frame data, and note any misfire, fuel trim or catalyst codes
  2. Identify which cylinder bank is Bank 2 and where Sensor 3 sits on this vehicle
  3. Inspect the sensor wiring and connector for chafing, melting, corrosion or water
  4. Check the exhaust for leaks near the sensor
  5. Watch the sensor signal in live data and see how it reacts to quick throttle snaps
  6. Test heater circuit power, ground and heater resistance
  7. Review short and long term fuel trims on Bank 2 and find the cause of any deviation
  8. If everything checks out, replace the sensor, clear the code and confirm it does not return

Common fixes

  • Replace the Bank 2 Sensor 3 oxygen sensor
  • Repair the wiring or connector
  • Fix the exhaust leak
  • Correct the cause of the wrong mixture (vacuum leak, injectors, fuel delivery)
  • Replace the catalytic converter if it is confirmed as the cause

Questions and answers

What does P019D mean?

The ECU found that the Bank 2 Sensor 3 oxygen sensor is too slow to respond when the mixture changes from lean to rich. The sensor itself, its wiring or an exhaust leak are the most common causes.

Can I drive with P019D?

Usually yes for a short time. Have it checked soon to avoid wasted fuel and excess emissions.

Do I always need a new sensor?

No. Check the wiring, connector, exhaust leaks and fuel trims first. Replace the sensor when those are ruled out or its signal is clearly sluggish.

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.