Thank you! This saved me, and was absolutely the cause of my P0101 and P2188 codes. I had already replaced MAF, checked PCV system, checked for vacuum/other leaks, and was about to replace the vacuum/temperature sensor. Cleaning the throttle body fixed the problem (even though it didn't look too dir...

Just chiming in to say a bit CHEERS for making this DIY. I just replaced my front O2 sensor, took me 45 min start to finish. Would have been who knows how long without your detailed instructions, so THANK YOU! One small thing to add - you don't need the 'proper' O2 socket (at least not on my 2005 XC...