I just replaced the proverbial intake and exhaust solenoids on my 2010 Equinox LT. After driving it around running errands for a bit, the check engine light came on. It threw 2 codes. P0420 and P0420 with two funny symbols after it. See photo. I used the OBD II reader and cleared the codes. Thoughts on this???
P0420 is catalyst efficiency, which could be any number of a hundred different causes, a failing catalyst only one of them.
I believe the symbols are for "pending" (which is different than a code that has set the CEL/SES check engine light. The second symbol I think is just an indication that there is more than one code, and you can use the arrow keys to page through them. Note that a P0420 and a pending P0420 are considered different codes, even though they represent the same thing.