2005 X5 4.4i Error Code P1434

[Beckerm4]

Hello all!

I'm new to the site having just purchased my X5 about two months ago. Recently, the SES light has illuminated. I connected the OBD II and it showed 2 codes, both p1434, aux emissions. A quick search came up with the most likely problem of a loose gas cap. I purchased a new cap for $20 and cleared the codes. A couple weeks later the SES light is on again with the same two codes. I've also seen this can be caused by a faulty leak detection pump. Is that my next move? Is there anything else I should check?

I believe the pump and other units are behind the rear passenger wheel well. Is that correct?

I should add that the vehicle runs fine.