Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.
There has been a service bulletin for that type of concern. Here is what it states.
MIL Illuminated - 3.0L V6 - False Flagging of DTC P1383 or P1388 - Reprogram PCM
Some 2000-01 MY S-TYPE vehicles may experience illumination of the MIL with DTCs P1383 or P1388 (over retarded camshaft timing) stored.
To eliminate the false flagging of DTCs P1383 and P1388, the Powertrain Control Module (PCM) should be re-programmed using WDS software release JTP759/14 or later.
When entering the ECM re-configuration section the user will be prompted to determine the engine serial number of the vehicle.
If the first six digits of the engine number are outside the specified serial number range (103981*** to 127908***) the user will be allowed through to re-calibrate the vehicle PCM with a standard set of calibrations.
If the engine serial number falls within the given range the system will automatically divert to a more aggressive set of calibrations.
In case of a customer complaint of the above condition on a 2000-01 MY S-TYPE vehicle within the above VIN range, follow the workshop procedure outlined below.
Harsh/Slow Shifts - 3.0L V6 Vehicles - Reprogram PCM
Customers of some 2000-01 MY S-TYPE vehicles may complain about harsh shifts or shifts that take too long to complete.
To improve harsh gear change, and the general performance of the automatic transmission, the Powertrain Control Module (PCM) should be re-programmed using the latest release (JTP759/14 or later) of the Worldwide Diagnostic System (WDS) disc.