SL500 Rough Idle, No Power, BAS Code

[cessna5354]

A friends 1998 SL500 needed a jump, would not start only clicking. Charged overnite and got it started in the AM. Would not idle smoothly or over 500 rpm, and BAS code displayed. No Power, floor accelerator no rpm's over 500.
Replaced battery, car starts great, but still no idle( or with it floored) over 500, and BAS code displayed.

Battery voltage (MB replacement) 12.47V. At idle, 14.17V.
Last thing done to the car was installation of Sirrius radio by pro shop.

Where should I look.?

Sorry All my experience is with diesels, first time with the great looking SL owner. The convertible looks good as well.

Thanks for your assistance,
Gary P