Day one at the Circuit de Catalunya would see Antonio Pizzonia and Marc Gené having to contend with wet weather early on. The conditions were to improve by late morning so the drivers could put in some useful test mileage. Antonio Pizzonia would complete seventy seven laps, with a best time of 1m:19.526 which was the second best time. Marc Gené focused on gathering engine data, completing twenty seven laps and finished the session on fourth position with a 1m:23.666.

The second day was run in brilliant sunshine, with Antonio Pizzonia and Marc Gené again carrying out the driving duties. Further test of the modified BMW P82 engine as well as set-up work for Indianapolis and Suzuka were the focus of the days activities.

At the end of the day it would be McLaren's Alex Wurz who would set the best time of the day with 1m:16.950. Antonio Pizzonia was second fastest with a 1m:17.747, after completing seventy nine laps. Marc Gené, whose contract has been prolonged by a year on Wednesday, was fifth with a best lap of 1m:19.707. Gené would complete forty one laps.

After the days testing Gene said: "I'm quiet happy with the course of the test. We slightly modified the chassis. Regarding aerodynamics we worked out some interesting results."

The team was again presented with excellent weather conditions on day three. Ralf Schumacher would join the other drivers, finishing the day with seventy four laps. Ralf would carry out tyre tests, as well as several aerodynamic adjustments were tested with Ralf trying different rear and front wings. The team also tested their traction control system.

Also present were the teams regular test drivers Marc Gené. Marc and Antonio completed nineteen and twenty eight laps respectively. Ralf set the fourth best time of the day with a 1m:18.886. McLaren's David Coulthard was the fastest with 1m:17.472. Gené and Pizzonia finished fifth and seventh respectively.

The teams 2003 engine, the BMW P83, was used for the first time. "Yesterday the P83 had his great roll out in Barcelona. We have already gathered important results", said BMW Motorsport Director Mario Theissen.

Dr Theissen added: "Our new P83 BMW engine for 2003 experienced its first roll-out during the Barcelona test and we are pleased how this went. On Wednesday and on Thursday we did run two of this new engines nearly 200 kilometres respectively.

Come Friday for the last day of testing the focus was on tyre testing. The team also tried various aerodynamic set-ups. BMW also loooked at their launch control system. Dr Theissen added: “And last but not least we have practiced launch control starts with different mappings in Barcelona."

The fastest time of the day was McLaren's David Coulthard with a lap of  1m:18.520. Antonio Pizzonia completed fifty nine laps to finish second with a best time of 1m:18.647. Marc Gené completed sixty three laps with a best time of 1m:19.118.

After the completion of the four day test the team came away feeling that the testing had been a success. Sam Michael, WilliamsF1 Chief Operations Engineer, commented on the test by saying: "Over the duration of the test, we trialled some new engine developments and specifications. We also evaluated tyres for the Suzuka Grand Prix, aerodynamic developments and traction control our four day programme has been a successful test of new development components."

Dr Mario Theissen added: "Our new P83 BMW engine for 2003 was rolled out for the first time during the Barcelona test and we are pleased with the outcome. On both Wednesday and Thursday we ran two of these new engines nearly 200 km each. On Friday morning we lost some track time due to a problem with one of the P82 engines.

"Apart from this, the test was about aerodynamic comparisons and tyres. Finally we have practiced launch control starts with different mappings in Barcelona."