Hello, new 2004 S40 1.9T bought last month with 77K miles.

I am installing an aux input accessory via the CD-changer port on the HU-555 radio. I am concerned about whether to disconnect the battery for the install. I have read about problems in doing so with or without battery disconnect. Seems that if you disconnect a component while battery connected (or cycling ignition) you get a code and light that dealer needs to reset. Alternately, I read that you sometimes get SRS warning lights on older cars when battery power dies/problems with SRS computer, etc. which also need dealer intervention. I have the radio code already so I have that covered.

I am looking for a quick EASY install with unnecessary dealer cost! What say you all?