I bought a 2001 Volvo S60. It was running well until it started showing the DSTC service warning, that appeared from time to time. Although I tested the battery, there were "low battery voltage" warnings. Then other warnings started appearing--no oil pressure; alarm service required and immobilizer warning. Now it has difficulty starting. The battery sometimes appears to be dead. Each time it starts,there are new warnings. In addition to that, the sunroof, windows and locks are not functioning anymore. Do you have any suggestion why this is happening? The previous owner never gave me the master key--could that be the cause of these malfunctions or is it just battery?
If the battery tested good, then I would suspect a problem with the alternator. The battery is basically just an electronic storage device that must be charged regularly by the alternator. In addition, there are a couple dozen modules aboard a Volvo and the must have adequate voltage for proper operation. When this happens, the instrument cluster will light up like a Christmas tree. I suggest you have a trained professional, such as one form YourMechanic, test your charging system to determine if the alternator has failed.