OBD II Code will not clear?
 

Hello all.

I recently replaced the O2 sensors on my 2005 volvo S40 2.4i. Cleared code by disconnecting neg. battery for half hour. Drove 3 days 300+ miles with no code, and went to get it inspected. While the car was hooked up during inspection, the old code came back on and I failed emissions test.

Is there a reason pulling the battery terminal didn't clear the code completely? I can't believe that it is a "coincidence" the light came on while under testing, especially after 300+ miles of driving.

Is there something special about clearing volvo codes that I am not aware of?

Thanks for everyone's help!

FYI I did read the faq's and I did search the database first before posting... with no responses, I went back and re-searched because I don't want to be "that guy". I cannot find anything specific to a code coming back while under testing.

I just purchased an OBD II code reader/eraser, so I'm hoping that will permanently remove the code from the memory, but if you know something I don't, please share your knowledge with me.

Thanks

Thank you all for your help. Couldn't have done it without you.

The scanner might not be able to clear all the codes.
You should have had the codes cleared properly from the start.
People do not seem to understand that disconnecting the battery does not clears the codes. It might turn the light off but the codes are still there.

Also most generic scanners only read half the codes on the newer cars.

Also after the code is cleared it needs to be driven the proper driving cycle to set the readiness to pass emissions.

Thank you...

I saw in the faq the short answer for disconnecting a battery... was looking for the long answer.

Just got my code reader in the mail, will try erasing the code and will post back for future reference

New codes came back, I just happened to have a new problem.