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O2 Sensor DTC Code with Engine Light Off

nrider

By nrider
in Ask A GM Technician

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nrider Enthusiast

nrider

Posted
Posted

So had the engine light come on about a week ago and after checking fluids and other things decided to buy a Performance Tool OBDII Scan tool to see what codes were causing the light to come on. Scanner reported that the fault was with one of the downstream o2 sensors. Trying to get the bolt to the o2 sensor off has been a pain and was about to head out to by some liquid wrench or other oil when I noticed the check engine light was now off after being on for a week.

 

I plugged in the Scan Tool again and even after a rescan it is still showing the o2 sensor fault but the engine light remains off.

 

Is it normal for the light to go out when the problem has not been fixed? Could the reading have been an error or misreading and now the OBD module is not picking up the problem yet the previous code remains in memory or history? The actual scan tool does not report the code as "Pending" or anything and also did a rescan. Could the colder weather last week (minus degrees celsius) cause it to seem there was a problem with the sensor when there was not and now having determined there isn't it has gone off?

 

Any info would be appreciated as to why code would remain with MIL off as I am unsure whether to continue to try and get the sensor off and buy a new one..or just wait and see if the light comes back on soon.

 

Thanks.

txab Senior Enthusiast

txab

Posted
Posted

Codes stays until it is cleared from memory. Clear it and see if it returns. Light does not have to stay on constantly for a code to be set and saved

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