Emissions

P015D — O2 Sensor Slow Response, Lean to Rich (Bank 2, Sensor 1)

Severity: medium Safe to drive

What P015D means

The engine control unit monitors how quickly the upstream oxygen sensor (Bank 2, Sensor 1) reacts when the mixture shifts from lean to rich. A healthy sensor switches almost instantly, and the computer uses that signal to fine-tune fuel delivery. P015D sets when the lean-to-rich transition is too slow. Bank 2 is the side of the engine that does not contain cylinder 1.

Symptoms

  • Check Engine light on
  • Worse fuel economy
  • Hesitation or sluggish acceleration
  • Unstable or rough idle
  • Higher exhaust emissions, possible emissions test failure

Possible causes

  1. Aged or contaminated Bank 2 Sensor 1 oxygen sensor
  2. Fault in the sensor heater circuit
  3. Damaged wiring or a poor connector at the sensor
  4. Exhaust leak upstream of the sensor
  5. Vacuum or intake leak, or another mixture problem on that bank
  6. Rarely, a PCM software or monitoring fault

How to diagnose

  1. Scan for codes and freeze-frame data, and note any other fuel trim or O2 sensor codes
  2. Compare short- and long-term fuel trims on Bank 2; a large positive or negative value points to a mixture problem
  3. Inspect the sensor wiring and connector for breaks, corrosion or heat damage
  4. Test the heater circuit for power and resistance
  5. Check the exhaust manifold and joints for leaks near the sensor
  6. Look for intake leaks: hoses, manifold gasket, vacuum lines
  7. Graph the sensor signal live and judge how quickly it switches
  8. Compare its behavior with the Bank 1 sensor if the engine has one

Common fixes

  • Replace the Bank 2 Sensor 1 oxygen sensor
  • Repair the wiring or replace the damaged connector
  • Seal exhaust leaks ahead of the sensor
  • Fix the vacuum leak or other cause of the wrong mixture
  • Update PCM software if a service bulletin applies to the vehicle

Questions and answers

What does P015D mean?

The front oxygen sensor on the second bank of cylinders is reacting too slowly when the mixture changes from lean to rich. The computer treats that response as too slow and stores the code.

Can I drive with P015D?

For a short time, yes, but fuel economy and emissions will get worse and the catalytic converter works under poorer conditions. Have it diagnosed soon.

Will replacing the sensor fix it?

Not always. Check the wiring, heater circuit, exhaust and vacuum leaks and fuel trims first, otherwise a new sensor may set 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.