This car has the worst am radio reception of any car I have ever owned and I have owned way too many cars! Is it an antenna issue or the head unit? It is the HU 850, other then the horrible am radio reception the sound is amazing!
TNN39-43-2004-04-19 Title: Grounding of Differential Electronic Module to Reduce A.M. Band Radio Interference
Owners of all wheel drive vehicles may report A.M. radio static or a crackling noise heard in areas of weak A.M. radio reception. The disturbance is especially noticeable during acceleration and can be related to the function of the Differential Electronic Module.
TNN39-49-2005-08-23 Title: AM - Radio Static on Turbo Cars, Caused by PEM. Analysis has found that the PWM (Pulse Width Communication) between the Engine Control Module (ECM) and the PEM (Pump Electric Module) can induce a whining noise on the lower frequencies of the AM-band.
I see references to some sort of brass strip that makes the am antenna coupling work better, but many of the threads on this issue are old and links are not good anymore. Here's a description:
Audio System - Poor AM Reception
S80 MY 99 ->, S60 MY 01 ->
Poor AM Reception
Service Bulletin 39-0018 and 39-0025
Cases have been reported in which AM static will increase and maintain a higher level resulting in complaints of poor AM reception. The increase in AM static may be triggered by several reasons including: bumps in the road closing the doors. The AM static will stop by several reasons including:
Central Door Lock activation rear defrost activation touching the trim covering the antenna amplifier.
It has been determine the increase in AM static is due to a loose connection between the antenna amplifier and antenna cable. To improve the connection (and AM reception) this Tech Net Note provides instructions to install a brass strip Part Number 30657370.
The brass strip must be bent as shown.
NOTE: It is critical not to exceed the 8 mm (5/16") length. If this length is exceeded it will result is worse reception.
Install the brass strip into the antenna amplifier as shown.
Install antenna cable so that the locking clips are not on top of the brass strip. It may help to push the locking clips to help seat properly.
NOTE: After the antenna cable has been installed pull the antenna cable to verity the locking clips are holding the antenna cable in the proper position. If the antenna cable releases easily the locking clips were not seated.