O2 Sensor Problem
O2 Sensor Problem Just got back from O'Reilly from doing a scan. Iv been getting an SES light on and off for the past month or two. It comes on for a bit, stays around for 200 or so miles, and resets itself and stays off for a few weeks and then will do it all over again. Iv scaned it before with the same results "P0133 O2 Sensor Circuit Slow Response Bank1, Sensor1". It came on the other day, scaned it and then replaced it with one of my old rear one (Have long tubes). Today the light was back on so I scaned it and got the same message. This time I monitored the system and started the car. The volts on Bank 2 were pretty constant at .4 but Bank 1 was all over the place from .1-.8. Eletrical problem? Thanks for any help.
Teching In
Joined: Dec 2004
Posts: 17
Likes: 0
From: Stockton Ca
02 sensors Hey hopefully this well help as I just had to sit through a california smog class where we had to learn about a bunch of emmissions crap.
The output from an O2 sensor should constantly cycle between high and low voltages as the engine is running in closed loop. This cycling is the result of the computer constantly correcting the air/fuel ratio in response to the feedback from the O2 sensor. If it is below .5 volts and remains constant it is reading a lean mixture, and if it reads above .5 volts and is constant it is reading a rich mixture.
When the O2 sensor reads lean, the computer will enrich the mixture, and
when the O2 sensor reads rich, the computer will lean the mixture. When the computer does this, it is in control of the air/fuel mixture.
The activity of the sensor can be monitored on a scanner.
Watch the scanner while the engine is running.
The O2 voltage should move to nearly 1 volt then drop back to close to zero volt. Immediately after it drops, the voltage signal should move back up. This immediate cycling is an important function of an O2 sensor.
If the response is slow, the sensor is lazy and should be replaced. With the engine at about 2,500 rpm, the O2 sensor should cycle from high to low ten to forty times in 10 seconds. The voltage readings shown on the scanner are also an indicator of how well the sensor works. When testing the O2 sensor, make sure the sensor is heated and the system is in closed loop.
The output from an O2 sensor should constantly cycle between high and low voltages as the engine is running in closed loop. This cycling is the result of the computer constantly correcting the air/fuel ratio in response to the feedback from the O2 sensor. If it is below .5 volts and remains constant it is reading a lean mixture, and if it reads above .5 volts and is constant it is reading a rich mixture.
When the O2 sensor reads lean, the computer will enrich the mixture, and
when the O2 sensor reads rich, the computer will lean the mixture. When the computer does this, it is in control of the air/fuel mixture.
The activity of the sensor can be monitored on a scanner.
Watch the scanner while the engine is running.
The O2 voltage should move to nearly 1 volt then drop back to close to zero volt. Immediately after it drops, the voltage signal should move back up. This immediate cycling is an important function of an O2 sensor.
If the response is slow, the sensor is lazy and should be replaced. With the engine at about 2,500 rpm, the O2 sensor should cycle from high to low ten to forty times in 10 seconds. The voltage readings shown on the scanner are also an indicator of how well the sensor works. When testing the O2 sensor, make sure the sensor is heated and the system is in closed loop.
Last edited by ricehater2000; May 6, 2007 at 02:56 AM. Reason: more imformation.
