Diagnostic mode means that you have successfully attached the scan tool and can read codes.

The LED on the recirc switch does not "tell" you anything of diagnostic value. It just starts to blink at 1HZ when you connect the scan tool. It will continue to blink steadily @ 1HZ until you turn off the key, even after you have removed the scan tool.

Perhaps it is confusing since none of the other computers you can scan cause anything to blink except the scan tool.

Just pretend like the recirc LED is not there...when it starts to blink after you connect the scan tool, it is meaningless. Probably would have been better if they had not programmed it to do that.

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2012 E350
2006 Callaway SC560