# 97 328is O2 sensor heater circuit malfuntion

**URL:** <https://forums.speedlife.net/t/97-328is-o2-sensor-heater-circuit-malfuntion/68796>\
**Category:** NYSpeed Automotive\
**Created:** [June 5, 2009, 1:05pm UTC](https://forums.speedlife.net/t/97-328is-o2-sensor-heater-circuit-malfuntion/68796 "2009-06-05T13:05:05Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![woz](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/woz/32/7605_2.png) [@woz](https://forums.speedlife.net/u/woz)\
**Post date:** [June 5, 2009, 1:05pm UTC](https://forums.speedlife.net/t/97-328is-o2-sensor-heater-circuit-malfuntion/68796/1 "2009-06-05T13:05:05Z")

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so i replaced my clutch about 2 months ago, after doing so i threw a CEL after starting it for the first time. the only thing i had disconnected was the **rear** 2 o2 sensors. they were disconnected for a few days while i was doing the clutch, tied up under the car (i know, not that good). i figured it was throwing it due to having the sensor disconnected at one point, or something like that i was hoping it would go away with time. it has not, so today i bought a scanner and sure enough its the 02 sensor. the code its giving me is o2 sensor heater circuit malfuntion for the 2 o2 sensors before the cat. now if it had just thrown one i would have replaced the o2 sensor already but both going at the same time seems strange. so i looked into it on bimmerforums some, seems a decent amount of other ppl have seen this issue, but theres no solid solution. a lot of ppl just get o2 sensor simulators, not something i want to do. i swaped the relays and have ruled that out, but was also told that my yr/model does not have a relay, its directly controlled by the computer. when i clear the codes they come back within 30seconds of the car running.

just looking for anyone to throw something else out there for me to check.