P0165 - OBD Trouble Code

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If you notice immediate effect on the drivability of the car like loss of engine power and acceleration, increased fuel consumption and Check Engine Light on along with ECM failure, there might be an OBD code P0165 in play.

The P0165 code means that the powertrain control module is not getting a right response from the O2 sensor.

This indicates that when the computer cuts the fuel to test sensor output, it does not respond quickly enough and the code is set. This can be caused by a problem with the O2 sensor or a problem with the exhaust catalyst getting too much fuel in the exhaust and not being able to burn it off in the catalyst fast enough. The PCM determines the lean to rich transition when the HO2S voltage changes from less than 300 mV to greater than 600 mV. The PCM determines the rich to lean transition when the HO2S voltage changes from more than 600 mV to less than 300 mV. An HO2S that responds too slowly is most likely defective.

What causes the problem of O2 Sensor Circuit Slow Response (B2 S3)?

• Heated Oxygen Sensor problem
• Faulty Oxygen Sensor Connectors
• Wiring and Harness issues with the sensors circuit
• Blown HO2 sensor fuses
• Faulty catalytic converter
• Excessive vacuum and exhaust leaks
• ECM sensor fault due to circuit or wiring damage

1. Heated Oxygen Sensor - The inadequate heating of the oxygen sensor immediately makes the ECM to go into failsafe mode due to failure of the fuel delivery system, and engine control module. Replace faulty sensors now!
2. Engine Control Module - ECM faults can store and display wrong OBD Code which can result in wrong diagnosis. Thus, replace the damaged components now.
3. Powertrain Control Module - PCM issues directly affects the engine control and transmission control module. Thus, replace faulty components now.
4. Catalytic Converter - Sometimes catalytic converters can overheat and become faulty. Replace your old catalytic converter now!
5. Mass Air Flow Sensor - The faulty MAF sensor will result in inefficient fuel delivery system and engine performance. Thus, replace faulty sensor now!
6. Exhaust Gas Temperature Sensor - This sensor, if faulty will wrongly measure the temperature of the air coming out of the combustion chamber and won’t be able to help in managing the air to fuel ratios. Thus, replace immediately, if found faulty.
7. Fuel Pump - An affected fuel pump will hamper the fuel delivery system and thus the engine performance. Replace damaged pumps immediately and always check for leaks.
8. Diagnostic Tool - Find wide range of diagnostic tools to detect and correct the OBD code error.
9. Manifold Absolute Pressure Sensor - Faulty MAP sensor affects the fuel economy, causes rough engine idles and failed emission tests. Thus, replace faulty MAP sensors now!

Possible symptoms from the O2 sensor heater failure include the O2 sensor not giving the proper reading as fast as it should, in which case the ECU (Engine Control Unit) would go into failsafe mode until the system is repaired. The Check Engine Light would then come on once the ECU detects the O2 sensor problem. The failsafe mode will cause different drive complaints, depending on the manufacturer programming.

Common Symptoms

• Prominent increase in the fuel consumption
• Engine stalling and not starting along with loss of power and response
• Visible white or black smoke from the tailpipe
• Over-fuelling over extended period of time causing dilution of engine oil
• Rough idle and hard starting of the engine
• Carbon deposit build up impacting the spark plugs

• Replacement of oxygen sensor(s)
• Repairing/Replacing wiring associated with the oxygen sensor
• Repairing vacuum leaks in exhaust system
• Replacement of the powertrain control module (PCM)

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• Some of the main diagnostic tools that are required to diagnose a code P0165 are a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable vehicle information source.
• Check and resolve for all engine misfire codes, throttle position sensor codes, manifold air pressure codes, and mass air flow sensor codes must be diagnosed and repaired.
• Always start with a visual inspection of system wiring harnesses and connectors. We 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.
• Use technical service bulletins (TSB) in your vehicle information source to resolve this error. 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.
• Retrieve all the data codes and freeze frame the data using the scanner. This information may be helpful if the P0165 proves to be intermittent so write it down for later. Now, clear the codes and see if the P0165 is reset.
• Start the engine, allow it to reach normal operating temperature, and then let it idle (with the transmission in neutral or park), if the code is reset. Use the scanner data stream to observe O2 sensor input data.
• Narrow the data stream display to include only pertinent data and you will see 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 P0165 will be stored.
• Connect the Digital Voltmeter Ohmmeter test leads to the sensor ground and signal wires in order to monitor live data from the O2 sensor.
• Also check the 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.

Common Mistakes When Diagnosing The P0165 Code

Use proper diagnostic tools and follow the complete diagnostic procedure without skipping any steps to avoid unneeded repairs and wrong diagnosis. Monitoring the sensor data from the scan tool live data stream is the only way to check for proper operation, and the sensor should not be replaced until it is tested.

Also, always check for damaged wiring and connections as well as PCM faults.