P015B – O2 Sensor Delayed Response – Lean to Rich

Stephen Darby

By Stephen Darby (Contact Me)
Last Updated 2019-04-21
ASE Master Tech

Trouble CodeFault LocationProbable Cause
P015B O2 Sensor Delayed Response – Lean to Rich Defective O2 sensor(s), Wiring, Defective catalytic converter, Engine exhaust leaks

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What Does Code P015B Mean?

A stored code P015B, simply means that the powertrain control module (PCM) has detected a delayed response time from the upstream (before the catalytic converter) oxygen (O2) sensor or circuit for engine bank one. Bank 1 indicates the bank of the engine which contains the number one cylinder.

Heated oxygen sensors are constructed with a zirconium dioxide sensing element. It is protected by a vented, steel housing. Platinum electrodes connect the sensing element to wire leads in the O2 sensor wiring harness. The harness is connected to the PCM through the controller area network (CAN). With the engine at normal operating temperature and running, the PCM is supplied with an electrical signal reflecting the percentage of oxygen particles in the engine exhaust compared to the oxygen content of ambient air. Exhaust gases exit the combustion chambers through exhaust manifold(s) and down pipe(s). Exhaust then flows through the O2 sensor vent holes (in the steel housing) and across the sensing element. Ambient air is drawn through the wire lead cavities where it is trapped in a small chamber in the center of the sensor. The trapped ambient air (in the chamber) is heated by the exhaust, forcing the oxygen ions to produce (energy) voltage. Varying degrees in the concentration of oxygen molecules in ambient air (drawn into the center cavity of the O2 sensor) and the concentration of oxygen ions in the spent exhaust gases, cause the heated oxygen ions inside the O2 sensor to jump between platinum layers very rapidly and repetitiously. Fluctuations in voltage occur as the rushing oxygen ions jump between the layers of the platinum electrodes. These variations in voltage are identified by the PCM as changes in exhaust oxygen concentration which indicate that the engine is either running lean (too little fuel) or rich (too much fuel).

When more oxygen is present in the exhaust (lean condition), the voltage signal from the O2 sensor is low and is higher when less oxygen is present in the exhaust (rich condition). This data is used by the PCM primarily to calculate fuel delivery and ignition timing strategy but also to monitor catalytic converter efficiency. If the O2 sensor in question fails to cycle as rapidly and/or regularly as expected, over a set period of time and under certain predetermined circumstances, a P015B code will be stored and a malfunction indicator lamp may be illuminated.

What are the common causes of code P015B?

  • Defective O2 sensor(s)
  • Burnt, broken, or disconnected wiring and/or connectors
  • Defective catalytic converter
  • Engine exhaust leaks

What are the symptoms of code P015B?

  • Diminished fuel efficiency
  • Reduced engine performance
  • Other related diagnostic trouble codes may also be stored
  • Service engine soon lamp illumination

How do you troubleshoot code P015B?

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable source of vehicle information will be required to diagnose and repair a P015B. All engine misfire codes, throttle position sensor codes, manifold air pressure codes, and mass air flow sensor codes must be diagnosed and repaired before trying to diagnose a code P015B.

A visual inspection of system wiring harnesses and connectors is a good place to begin. Focus on harnesses that are routed near hot exhaust pipes and manifolds, as well as those that are routed near sharp edges like the ones found on exhaust shields. Make repairs as needed.

Search technical service bulletins (TSB) in your vehicle information source. If you find one that matches the symptoms and code/s presented by the vehicle in question, it will very likely aid you in your diagnosis. TSB listings are compiled from thousands of successful repairs.

Connect the scanner to the vehicle diagnostic port and retrieve all stored trouble codes and freeze frame data. Write this information down as it may prove helpful later. Once this is done, clear the codes and see if the P015B is reset.

If the code is reset, start the engine and allow it to reach normal operating temperature. Let the engine idle (with the transmission in neutral or park). Use the scanner data stream to observe O2 sensor input data. Narrowing the data stream display to include only pertinent data will net a faster and more accurate data response. If the engine is running efficiently, upstream O2 sensor data should fluctuate regularly between 1-millivolt (.100-volts) and 9-millivolts (.900-olts). If voltage fluctuations are slower than expected, a P015B will be stored.

Use caution when using the DVOM near hot exhaust components. Connect the DVOM test leads to the sensor ground and signal wires in order to monitor live data from the O2 sensor. You may also use it to check resistance of the O2 sensor in question, as well as voltage and ground signals. To prevent control module damage, disconnect related controllers prior to testing system circuit resistance with the DVOM.

Codes Related to P015B

  • P0173 Lean Exhaust Bank 1
  • P0174 Lean Exhaust Bank 2
  • P013E O2 Sensor Delayed Response – Rich to Lean (Bank 1 Sensor 2)
  • P013F O2 Sensor Delayed Response – Lean to Rich (Bank 1 Sensor 2)
  • P014A O2 Sensor Delayed Response – Rich to Lean (Bank 2 Sensor 2)
  • P014B O2 Sensor Delayed Response – Lean to Rich (Bank 2 Sensor 2)
  • P015A O2 Sensor Delayed Response – Rich to Lean (Bank 1 Sensor 1)
  • P015C O2 Sensor Delayed Response – Rich to Lean (Bank 2 Sensor 1)
  • P015D O2 Sensor Delayed Response – Lean to Rich (Bank 2 Sensor 1)

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