Check engine light

FREIGHTDOG2007

MEMBER
2010 GMC ACADIA
2.6L
6 CYL
2WD
AUTOMATIC
50,000 MILES

Light illuminates and scan reads secondary oxygen sensor unable to make adjustment. Since there are bank 1 and bank 2, the problem indicates bank 2. There are also two oxygen sensors in each bank. Does the primary O2 sensor control the fuel air to the PMC and the secondary just verify that the primary is doing its job? Battle plan, change primary and see if problem returns? Or change bank 2 primary and secondary sensors as a pair?

5 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good morning,

Lets start with the code first. There are way too many codes for the sensors to say to replace it.

The upstream is the one that controls fuel mapping. The downstream has only one job, that is, to monitor the catalytic converter. It does not have a say in fuel mapping.

Roy

https://www.2carpros.com/articles/how-an-oxygen-sensor-works

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Monday, November 26th, 2018 AT 4:06 AM

FREIGHTDOG2007

MEMBER
3 POSTS

Thank you Roy. That was along the lines of my train of thought. Since the overview I read of how it works, it was mentioned that 80,000 was the general life expectancy. I am over here in the Middle East so I have got both Upstream and Downstream ordered and on the way. Since the Bank 2 is up front and in sight, I will change that one. By the way, the code was 2099 with no other codes. At least the catalytic converter is still okay. Or at least I hope.

Thanks again.

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Monday, November 26th, 2018 AT 4:19 AM

ASEMASTER6371