PO131 code on Pontiac Montana

[rmorton]

I have a 2003 Montana with 230k miles. When I accelerate really hard to pass (particularly uphill) the SES light comes on and the PO131 code is thrown. I can clear it and drive without issue until the next hard acceleration. There is no trouble idling or running - just the light and the code. Since the 02 sensor before the cat is hard to get to, I would like to try and confirm that its bad before I attempt replacing it. My question is this: is there a way to further test or confirm a bad O2 sensor without pulling it? I have a Tech II but I'm a complete novice at using it. Wondering if freeze frame info would help me? Never used the freeze frame data before...

[MKMike]

The code indicates low voltage from the O2 sensor, which can be anything from a faulty O2 sensor to an intake gasket issue.

This site has great step by step troubleshooting info.
http://troubleshootmyvehicle.com/gm/3.8 ... n-sensor-3

I'd heed the TechInfo advice to only buy Denso or ACDelco when shopping for a replacement sensor, if that is the cause.

[rmorton]

Thank you for the help Mike!

[MKMike]

You're welcome.
Hope it's something simple.
Do let us know what it was caused by.

[CMNTMXR57]

If you rule out O2 sensors and are sure that there are no post-MAF intake leakes, check/clean your MAF.

If I recall, a Montana uses a barrell style MAF sensor, and the Thermistors are prone to getting dirty and/or sooted up should you be using aftermarket oilable filters.

FYI, P0131, is a universal standard code for all manufacturer's, and for GM is the same design theory on all GM vehicles. Doesn't matter if it's a Montana or my V. What may be different is the actual troubleshooting steps, but the theory remains the same. The point being, you could do a search on P0131 here, and even though it's a Bonneville, the overall concept is the same.