# Actron - Oxygen Sensor Monitor Question **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [November 12, 2008, 7:19pm UTC](https://community.cartalk.com/t/actron-oxygen-sensor-monitor-question/22013 "2008-11-12T19:19:12Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Edziu63](https://avatars.discourse-cdn.com/v4/letter/e/f17d59/32.png) [@Edziu63](https://community.cartalk.com/u/Edziu63)\ **Post date:** [November 12, 2008, 7:19pm UTC](https://community.cartalk.com/t/actron-oxygen-sensor-monitor-question/22013/1 "2008-11-12T19:19:12Z")
I have a 2000 Ponitac Grand Am it keeps throwing a P440 code. I have a Actron OBD II scanner and after I ersae the code and check the scanner, it tells me the oxygen sensor monitor is incomplete. Can someone tell me what this means? ---
**Author:** ![TwinTurbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TwinTurbo](https://community.cartalk.com/u/TwinTurbo)\ **Post date:** [November 12, 2008, 7:26pm UTC](https://community.cartalk.com/t/actron-oxygen-sensor-monitor-question/22013/2 "2008-11-12T19:26:07Z")
The monitor runs in the background and checks to see if, after a predetermined protocol has been met, that the O2 sensor is performing correctly and no failure codes are recorded. The purpose of the monitor is to prevent people from removing power, clearing the stored failure codes and then passing an inspection even though a known fault exists. The protocol for the O2 monitor varies between manufacturers but usually involves a number of start cycles and driving conditions in order for it to be set ready. Doesn’t the manual that came with your scanner describe this in detail? ---
**Author:** ![Edziu63](https://avatars.discourse-cdn.com/v4/letter/e/f17d59/32.png) [@Edziu63](https://community.cartalk.com/u/Edziu63)\ **Post date:** [November 12, 2008, 7:31pm UTC](https://community.cartalk.com/t/actron-oxygen-sensor-monitor-question/22013/3 "2008-11-12T19:31:43Z")
TwinTurbo, I’m not sure it does, but I’ll check the manual again. Is there somewhere on the internet that explains stuff like this??? ---
**Author:** ![oldschool](https://avatars.discourse-cdn.com/v4/letter/o/e19adc/32.png) [@oldschool](https://community.cartalk.com/u/oldschool)\ **Post date:** [November 12, 2008, 8:09pm UTC](https://community.cartalk.com/t/actron-oxygen-sensor-monitor-question/22013/4 "2008-11-12T20:09:56Z")
Your not asking for help to stop this code from being generated, so… ---
**Author:** ![Edziu63](https://avatars.discourse-cdn.com/v4/letter/e/f17d59/32.png) [@Edziu63](https://community.cartalk.com/u/Edziu63)\ **Post date:** [November 12, 2008, 8:46pm UTC](https://community.cartalk.com/t/actron-oxygen-sensor-monitor-question/22013/5 "2008-11-12T20:46:25Z")
How can I stop this code from happening? ---
**Author:** ![Cougar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cougar/32/21348_2.png) [@Cougar](https://community.cartalk.com/u/Cougar)\ **Post date:** [November 12, 2008, 9:26pm UTC](https://community.cartalk.com/t/actron-oxygen-sensor-monitor-question/22013/6 "2008-11-12T21:26:40Z")
I don’t really like erasing codes most of the time. If things are working as they should the error will be reset by itself after some running cycles. Like TT stated, it erases the set monitors and they need time to reset again. If you are in a state that requires an IM test, the test station will need to have a minimum of the monitors set in order to run the test. You may be able to find some good info on the “How Stuff Works” site about OBD2 systems. The code you gave isn’t a valid one. I assume you meant P0440 which is for the evaporative emission system. This problem could be due to just a simple loose gas cap. The air leak could be located elsewhere in the fuel line system also.