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P015D Code: Causes and How to Fix the Engine Error Code 

  • Cars Explained
  • Gerard Stevens
  • 5 minutes

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So, is your car lacking engine performance or low fuel efficiency? These are the common symptoms of many diagnostic trouble codes (DTC). A quick way to find the issue if your car has engine-related problems is with an OBD-II scanner. So, the scanner displays a P015D code when you check for the issue. How serious is this issue?  

Your car will activate the code when there’s a need to change a broken oxygen sensor, which can lead to a cracked catalytic converter. You need to fix the code at the earliest as it may cause severe issues to your car.  

So, what causes the P015D code to activate? What are its symptoms? How can you fix it? Keep reading to know about this DTC in detail via our blog! 

What does code P015D mean? 

The P015D code denotes ‘O2 sensor delayed reaction – lean to rich. When the oxygen sensor in the car doesn’t return data that the PCM typically anticipates, the error code appears. The powertrain control module (PCM) expects the oxygen sensor to provide data at predefined intervals.  

For the PCM to operate the engine effectively, it needs data from the oxygen sensors. The PCM won’t be able to calculate the appropriate values for factors like the air-fuel ratio and ignition timing if the oxygen sensor develops problems. This specific code is associated with oxygen sensor 1, which examines engine bank 2’s exhaust gases. 

Be aware that your car manufacturer may have a different meaning when the code appears. So, always ensure to check it when the code appears.  

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How serious is the P015D code? 

Since it indicates that the oxygen sensor was slow or unresponsive for longer, you should take the error code seriously. It will be best if you diagnose and fix the code at the earliest when it activates.  

What causes a P015D code? 

Several problems might trigger the P015D code, even though it is classified as an oxygen sensor issue. The following are some factors that could activate the code.  

  • A damaged catalytic converter. 
  • Faulty oxygen sensor.  
  • Leakage in the exhaust.  
  • Failure in PCM.  
  • Wire or connectors that got burned, damaged, or disconnected. 

What are the symptoms of the P015D code? 


The severity of the code is high as the O2 sensor has been slow or unresponsive for an extended period. The typical symptoms of this error include the following.  

  • Decrease in fuel efficiency. 
  • Lack of engine performance.  
  • Check engine light illuminates.  
  • Other engine error codes related to the oxygen sensor.  

How to diagnose P015D code 

You need to identify and fix all engine misfire codes, throttle position sensor codes, manifold air pressure codes, and mass air-flow sensor codes before attempting to troubleshoot the P015D code. A poorly performing engine will result in various codes getting saved (and rightly so). Professional technicians frequently begin by visually checking the connectors and wiring harnesses of the system.  

Look through your car’s information source for technical service bulletins (TSB). Finding one that fits the symptoms or codes displayed by the in-question car will probably help you make a diagnosis. Thousands of successful repairs form the basis of TSB listings. 

What to do 

  • Connect a scanner to the car’s diagnostic port and retrieve all frozen frame information and stored error codes.  
  • Check to check if the P015D resets after clearing the codes. First, start the engine, let it warm to normal operating temperature, then let it idle to see if the code gets cleared. 
  • Observe the O2 sensor input data via the scanner data stream. You will notice a quicker and more accurate data response if you narrow the data stream display to show relevant data. Upstream O2 sensor data should often vary between one millivolt (.100 volts) and nine (.900 volts) millivolts if the engine operates efficiently.  
  • The error code gets saved if voltage fluctuations are slower than anticipated. To view real-time data from the O2 sensor, connect the DVOM test leads to the sensor’s ground and signal wires. Disconnect relevant controllers before using the DVOM to check the system circuit resistance.  

Why you need to be careful 

  • Downstream O2 sensors shouldn’t cycle as frequently as upstream O2 after the PCM enters a closed loop operation.  
  • Avoid using low-quality replacement (or refurbished) catalytic converters because they are prone to frequent failure. 

How can you repair the P015D code? 

These are some steps to repair the DTC. 

  • Skilled technicians will use the scan tool to access the P015D code contained in the ECU.  
  • Technicians will note the presence of the P015D code and any associated freeze frame data. 
  • After all, the code will clear if the engine problem resolves. 

The PCM receives the information required to track transmission performance from the fluid pressure sensor. The electrical voltage measurement from the pressure sensor will rise with rising fluid pressure; fall with falling fluid pressure. Over time, this may cause engine parts to deteriorate. So it is better that you immediately plug any engine leaks. 

A flaw in how the engine produces gasoline frequently causes increased fuel consumption. The problem gets more critical when combined with the presence of a check engine light and other engine-related symptoms.  

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