2005 Honda Civic LX, auto trans, 185k+miles has a persistent P0134 code. I have replaced the suspect air/fuel sensor (bank 1, sensor 1) twice (second time was by the Honda dealership with OEM). PCM has been replaced twice as well. Honda dealership has troubleshot and indicated that wiring between the sensor and PCM is good and recommended replacing the PCM, which I did and the code persists. Engine idles high, near 1.1k and fuel mileage is not ideal due to this issue. What am I missing?
What am I missing?
You really shouldn't be taking a nearly 20-year-old car to a dealer for service. Most of the technicians there were probably in diapers when that car was built and they tend to be parts changers.
See the technical description of that code. It can be caused by external issues such as an exhaust leak or cracked exhaust manifold preventing the O2 sensor from responding quickly enough to satisfy the PCM's programming.
https://www.obd-codes.com/p0134
"The powertrain control module (PCM) provides a baseline voltage of about 450 mV on the oxygen sensor signal circuit. When cold, the PCM detects the the internal resistance of the sensor is high. As the sensor warms up the resistance is lowered and it starts producing voltage based on the oxygen content in the exhaust. When the PCM determines that the time it took for the sensor to warm up is greater than one minute or that the voltage is inactive (not reading outside 391-491 mV it views the sensor as inactive or open and sets the P0134 code."
Read more at: https://www.obd-codes.com/p0134
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