Swapping some exhaust over between bikes right now. I paid to have the exhaust installed on my '13 FLHR last year. Judging by the placement of the wires on the two bikes I'm swapping, the O2 sensor wires appear to be reversed. Both bikes have 4-wire sensors, black/grey/white/purple. No markings on either sensor. Wondering if it's possible the tech accidentally swapped them last year by mistake. How do I identify the correct order?

 

Black plug - rear cylinder
Grey plug - front cylinder

 

Thanks. Awesome. They've been swapped backward for a year. Maybe that explains the 36mpg i've been getting.

 

Black is back